C struct error objects can be created directly only in C.
C-side increments their reference counter when pushes to the Lua
stack.

It is not going to be so convenient soon. error_unpack() function
will be used in netbox to decode error object via Lua FFI.

Such error object will have 0 refs and no Lua GC callback
established. Because it won't be pushed on Lua stack natually,
from Lua C. To make such errors alive their reference counter
will be incremented and error_unref() will be set as GC callback.

Follow up for #4398

Co-authored-by: Vladislav <Shpilevoy&lt;v.shpilevoy@tarantool.org>

Part of #4398

@TarantoolBot document
Title: Custom error types for Lua errors

Errors can be created in 2 ways: `box.error.new()` and `box.error()`.

Both used to take either `code, reason, <reason string args>` or
`{code = code, reason = reason, ...}` arguments.

Now in the first option instead of code a user can specify a
string as its own error type. In the second option a user can
specify both code and type. For example:

```Lua
box.error('MyErrorType', 'Message')
box.error({type = 'MyErrorType', code = 1024, reason = 'Message'})
```
Or no-throw version:
```Lua
box.error.new('MyErrorType', 'Message')
box.error.new({type = 'MyErrorType', code = 1024, reason = 'Message'})
```
When a custom type is specified, it is shown in `err.type`
attribute. When it is not specified, `err.type` shows one of
built-in errors such as 'ClientError', 'OurOfMemory', etc.

Name length limit on the custom type is 63 bytes. All what is
longer is truncated.

Original error type can be checked using `err.base_type` member,
although normally it should not be used. For user-defined types
base type is 'CustomError'.

For example:
```
tarantool> e = box.error.new({type = 'MyErrorType', code = 1024, reason = 'Message'})
---
...

tarantool> e:unpack()
---
- code: 1024
  trace:
  - file: '[string "e = box.error.new({type = ''MyErrorType'', code..."]'
    line: 1
  type: MyErrorType
  custom_type: MyErrorType
  message: Message
  base_type: CustomError
...
```

API is different from box.session.push() - sync argument was
removed. It will disappear from Lua API as well, because it just
is not needed here. Session is omitted as well. Indeed, a user
can't push to a foreign session, and the current session can be
obtained inside box_session_push(). And anyway session is not in
the public C API.

Internally dump into iproto is done using obuf_dup(), just like
tuple_to_obuf() does. obuf_alloc() would be a bad call here,
because it wouldn't be able to split the pushed data into several
obuf chunks, and would cause obuf fragmentation.

Dump into plain text behaves just like a Lua push - it produces a
YAML formatted text or Lua text depending on output format. But to
turn MessagePack into YAML or Lua text an intermediate Lua
representation is used, because there are no a MessagePack -> YAML
and MessagePack -> Lua text translators yet.

Closes #4734

@TarantoolBot document
Title: box_session_push() C API

There is a new function in the public C API:
```C
    int
    box_session_push(const char *data, const char *data_end);
```

It takes raw MessagePack, and behaves just like Lua
`box.session.push()`.

box.session.storage is a general-purpose table, which can be
used by user. Therefore, we shouldn't store any internal details
in it.

Needed for #4686

A special format for encoding UUIDs to MsgPack is introduced.
It is supported by both lua and C encoders/decoders, and it is now
possible to insert UUIDs into spaces, but only into unindexed fields
without format for now.

Prerequisite #4268

@TarantoolBot document
Title: Internals: msgpack format for UUID

UUID values share the MessagePack type with decimals:
both use MP_EXT. A new subtype is introduced for UUIDs,
MP_UUID = `0x02`
UUID is encoded as follows:
```
    +--------+---------+-----------+
    | MP_EXT | MP_UUID | UuidValue |
    +--------+---------+-----------+
```
Since UUID is 16 bytes in size, the header, MP_EXT, is always the same:
`0xd8`. MP_UUID = `0x02` follows. The header is followed by the 16
bytes of the UuidValue.

UuidValue consists of 11 fields, which are encoded as big endian
unsigned integers in the following order: `time_low` (4 bytes), `time_mid`
(2 bytes), `time_hi_and_version` (2 bytes), `clock_seq_hi_and_reserved` (1
byte), `clock_seq_low` (1 byte), `node[0], ..., node[5]` (1 byte each).

The total size of such a representation is 18 bytes, whereas storing
uuids as strings requires from 34 (when '-'s are ommitted) to 38 bytes
per UUID, giving a 2x space usage improvement.

In terms of implementation, now struct error objects can be organized
into double-linked lists. To achieve this pointers to the next and
previous elements (cause and effect correspondingly) have been added to
struct error. It is worth mentioning that already existing rlist and
stailq list implementations are not suitable: rlist is cycled list, as a
result it is impossible to start iteration over the list from random
list entry and finish it at the logical end of the list; stailq is
single-linked list leaving no possibility to remove elements from the
middle of the list.

As a part of C interface, box_error_add() has been introduced. In
contrast to box_error_set() it does not replace last raised error, but
instead it adds error to the list of diagnostic errors having already
been set. If error is to be deleted (its reference counter hits 0 value)
it is unlinked from the list it belongs to and destroyed. Meanwhile,
error destruction leads to decrement of reference counter of its
previous error and so on.

To organize errors into lists in Lua, table representing error object in
Lua now has .prev field (corresponding to 'previous' error) and method
:set_prev(e). The latter accepts error object (i.e. created via
box.error.new() or box.error.last()) and nil value. Both field .prev and
:set_prev() method are implemented as ffi functions. Also note that
cycles are not allowed while organizing errors into lists:
e1 -> e2 -> e3; e3:set_prev(e1) -- would lead to error.

Part of #1148

This patch introduces "current" function for sequences.
It returns the last retrieved value of specified sequence or
throws an error if no value has been generated yet.

This patch partially reverts 3ff1f1e3
(box: remove sequence_get) here similar function "get" was removed
to avoid possible misleading with "currval" function of PosgreSQL
that returns the last obtained value of the sequence in the scope
of current session. In contrast "current" returns the last globally
retrieved value of the sequence.

Closes #4752

Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Nikita Pettik <korablev@tarantool.org>

@TarantoolBot document
Title: sequence:current()

This patch introduces "current" function for sequences.
It returns the last retrieved value of specified sequence or
throws an error if no value has been generated yet ("next"
has not been called yet or right after "reset" is called).

Lua:

Example:

```lua
sq = box.schema.sequence.create('test')
---
...
sq:current()
---
- error: Sequence 'test' is not started
...
sq:next()
---
- 1
...
sq:current()
---
- 1
...
sq:set(42)
---
...
sq:current()
---
- 42
...
sq:reset()
---
...
sq:current()  -- error
---
- error: Sequence 'test' is not started
...
```

C API:

```C
int
box_sequence_current(uint32_t seq_id, int64_t *result);
```

Where:
  * seq_id - sequence identifier;
  * result - pointer to a variable where the current sequence
  value will be stored on success.

Returns 0 on success and -1 otherwise. In case of an error user
could get it via `box_error_last()`.

All lua types feature check, push and is functions. We expose lua_checktuple
for full consistency.

Closes #2553

This patch adds the methods necessary to encode and decode decimals to
MsgPack. MsgPack EXT type (MP_EXT) together with a new extension type
MP_DECIMAL is used as a record header.

The decimal MsgPack representation looks like this:
+--------+-------------------+------------+===============+
| MP_EXT | length (optional) | MP_DECIMAL | PackedDecimal |
+--------+-------------------+------------+===============+
The whole record may be encoded and decoded with
mp_encode_decimal() and mp_decode_decimal(). This is equivalent to
performing mp_encode_extl()/mp_decode_extl() on the first 3 fields and
decimal_pack/unpack() on the PackedDecimal field.

It is also possible to decode and encode decimals to msgpack from lua,
which means you can insert decimals into spaces, but only into unindexed
fields for now.

Follow up #692
Part of #4333

These function are going to yield in scope of #4250, because
swim:new() will start a fiber, while swim:delete() cancels and
gives it a control.

Needed for #4250

Encryption with an arbitrary algorithm and any mode with a
configurable private key.

Closes #3234

Users of Lua SWIM module likely will use Lua objects as a
payload. Lua objects are serialized into MessagePack
automatically, and deserialized back on other instances. But
deserialization of 1.2Kb payload on each member:payload()
invocation is quite heavy operation. This commit caches decoded
payloads to return them again until change.

A microbenchmark showed, that cached payload is returned ~100
times faster, than it is decoded each time. Even though a tested
payload was quite small and simple:

    s:set_payload({a = 100, b = 200})

Even this payload is returned 100 times faster, and does not
affect GC.

Part of #3234

SWIM as a library can be useful not only for server internals,
but for users as well. This commit exposes Lua bindings to SWIM
C API. Here only basic bindings are introduced to create, delete,
quit, check a SWIM instance. With sanity tests.

Part of #3234

Static allocator gives memory blocks from cyclic BSS memory
block of 3 pages 4096 bytes each. It is much faster than
malloc, when a temporary buffer is needed. Moreover, it does not
complicate GC job. Despite being faster than malloc, it is still
slower, than ffi.new() of size <= 128 known in advance (according
to microbenchmarks).

ffi.new(size<=128) works either much faster or with the same
speed as static_alloc, because internally FFI allocator library
caches small blocks and can return them without malloc().

A simple micro benchmark showed, that ffi.new() vs
buffer.static_alloc() is ~100 times slower on allocations of
> 128 size,  on <= 128 when size is not inlined.

To better understand what is meant as 'inlined': this

    ffi.new('char[?]', < <=128 >)

works ~100 times faster than this:

    local size = <= 128
    ffi.new('char[?]', size)

ffi.new() with inlined size <= 128 works faster than light, and
even static allocator can't beat it.

crypto.lua is a public module using OpenSSL directly. But now
lib/crypto encapsulates OpenSSL with additional checks and
similar but more conforming API. It allows to replace OpenSSL
cipher in crypto.lua with lib/crypto methods.

Tarantool has a strict rule for naming methods of libraries - use
the library name as a prefix. For crypto lib methods it should be
'crypto_', not 'tnt_'.

Needed for #3276.

It's OK to use json format with the boot logger. As for syslog, let's
add a check to Lua's log_format() so that it fails gracefully rather
than raising an assertion.

Closes #3946

Add optional 'chars' parameter to string.strip, string.lstrip
and string.rstrip for specifying the unwanted characters.
Behavior modeled after the equivalent Python built-ins.

Closes: #2977

@TarantoolBot document
Title: string.strip(inp, chars)
Update the documentation for string.strip,
string.lstrip and string.rstrip to reflect
the addition of the optional param.

Make os.exit() call tarantool_exit(), just like the signal handler does.
Now on_shutdown triggers are not run only when a fatal signal is
received.

Closes #1607

@TarantoolBot document
Title: Document box.ctl.on_shutdown triggers
on_shutdown triggers may be set similar to space:on_replace triggers:
```
box.ctl.on_shutdown(new_trigger, old_trigger)
```
The triggers will be run when tarantool exits due to receiving one of
the signals: `SIGTERM`, `SIGINT`, `SIGHUP` or when user executes
`os.exit()`.

Note that the triggers will not be run if tarantool receives a fatal
signal: `SIGSEGV`, `SIGABORT` or any signal causing immediate program
termination.

Closes #3311

Fixing build under FreeBSD:
Undefined symbol "iconv_open"
Add compile time build check with FindICONV.cmake
and a wrapper to import relevant symbol names with include file.

Closes #3441

`lua_tostring`/`lua_tolstring` ignores metatable/boolean/nil and return NULL,
but sometimes it's needed to have similar behaviour, like lua functions
tostring. Lua 5.1 and LuaJIT ignores it by default, Lua 5.2 introduced
auxilary function luaL_to(l)string with supporting of __tostring. This
function is backport of Lua 5.1 "lauxlib.h"s luaL_tostring in the luaT
namespace.

Resolves #3284.

`sql_current_time` is exported only in debug mode and used to check
builtin datetime sql functions behavior in specific time moments.

Extra changes:
 * table-14.1 test is deleted, as it does not test anything.
   It was testing ddl inside of a transaction. This case is checked
   by 14.2 by now.

Closes #2646

Filed gh-3311 to remove this export soon.

Fixes #3310.

So that it can be used not only for serializing a list of tuples, but
also for serializing a Lua stack that stores output of CALL/EVAL.

Needed for #946

* Add struct log
* Add possibility to add logger configuration to global scope
* Refactor functions in say to use them with specified config,
 not only global variable

 This patch was inspired by need of additional logger in audit log
 Relates #2912

* Add log_format option to box.cfg{}
* Add json format in logging
* Add table converting to json in lua logging

Closes #2795

- Remove sqlite3BitvecBuiltinTest from export.

Savepoint allows to partialy rollback a transaction. After
savepoint creation a transaction owner can rollback all changes applied
after the savepoint without rolling back the entire transaction.

Multiple savepoints can be created in each transaction. Rollback to
a savepoint cancels changes made after the savepoint, and deletes all
newer savepoints.

It is impossible to rollback to a savepoint from a substatements level,
different from the savepoint's one. For example, a transaction can not
rollback to a savepoint, created outside of a trigger, from a trigger body.

Closes #2025

fiber_time() reports real time, which shouldn't be used for calculating
timeouts as it is affected by system time changes. Add fiber_clock()
based on ev_monotonic_now(), export it to Lua, and use it instead.

Needed for #2527

A part of #1451

Add `sqlite3BitvecBuiltinTest` to exported symbols to expose
it to ffi. Bug #2590 submitted to remove it from exports.

Fiber attributes are a way to specify parameters that is different
from the default. When a fiber is created using fiber_new_ex(),
an attribute object can be specified to configure custom values for
some options. Attributes are specified only at fiber creation time;
they cannot be altered while the fiber is being used.

Currently only stack_size attribute is supported. Fibers with
non-default stack size won't be recycled via fiber pool.

API overview:

* fiber_new_ex() creates a fiber with custom attributes.
* fiber_attr_new()/fiber_attr_delete() creates/destroys attributes.
* fiber_attr_setstacksize()/fiber_attr_getstacksize() sets/gets
  the fiber stack size.
* fiber_self() returns current running fiber.

All new functions are available from public C API for modules.

See #2438

`sql_schema_put` is a static function and should not be exported.
This routine was exported on early stages of SQL development
when DDL was non-functional at all and came to the top due to
patches re-mix.

SQL tests works just fine on current stack sizes, so revert
commit `sql: Run SQL compiler on large stack` and run
SQL compiler (entry is `sqlite3LockAndPrepare(...)`) on top
of caller's stack.