This chage removes SQL's WAL support. Most of code
related to it was removed. OP_Checkpoint op-code was
commented, but not removed (also PRAGMA wal_mode): this might
be useful in future if Tarantool's WAL is adopted there.

* Changes to sqltester:
  - Change lsearch to be closer to tcl implementation:
      return index of first match or return -1
  - Make execsql2 work with multistatements
* Converted tests include cases for large (64b) integers

Part of #2381

Big numvers return from sql to lua as double or as long long depending on it's
size (wheather it fit into mantisa or not)
Remember, in tarantool you can create variable of type long long using LL
postfix (ex: 1235453452343LL)

closes #2469

Now the _truncate space is being filled lazy.

Follow up 15a9af26

exp2(64) <= UINT64_MAX is true due to type conversion.
Use exp2(64) instead of UINT64_MAX (optimized out even on -O0).

Fixes buggy box/indices_any_type.test.lua on x86_64

Closes #2472

ffi.new('long', x) and ffi.new('unsigned long', x) uses arbitratry
user-defined ctypeid instead of built-in CTID_INT32 and CTID_UINT32.
Our tonumber64() implementation is not ready for that. Remove these
two test cases and move forward. Nobody cares.

Fixes box/misc.test.lua on i386 and armhf

Follow up #2459

lua_tointeger() is equivalent to (ptrdiff_t)lua_tonumber(L),
which causes precision loss on 32-bit systems when you expect
to get a proper uint32_t value. LuaJIT stores numbers as doubles,
so lua_tointeger() makes absolutely no sense.

Replace lua_tointeger() with lua_tonumber() everywhere except
cases when result is converted to int or lua_Integer.

Fixes box/indices_any_type.test.lua on i386 and armhf

Closes #2459

It is unsafe, because system spaces use triggers to keep records in sync
with internal objects while space truncation doesn't invoke triggers.

Closes #2523

Currently, space.create must insert an entry into 'truncate' system
space - if it does not, space.truncate won't work. This is incontinent,
as it makes it impossible to create spaces by simply inserting a tuple
into the 'space' system space via iproto API. So let's insert entries
into truncate space lazily, on the first space truncation.

Closes #2524

Space truncation is implemented as recreation of a space and all its
indexes. On success the original space is deleted by the commit trigger,
while on failure the new space is deleted by the rollback trigger. The
commit/rollback triggers are always called before commit/rollback engine
methods, which makes space truncation incompatible with transactions:
engine commit/rollback may access a space that have already been deleted
by commit/rollback trigger installed by space truncation, resulting in a
crash. So let's forbid to use space.truncate from a transaction until
triggers are made transaction-friendly.

Closes #2525

Closes #2531

Part of #2507

In order of xrow library creating, exceptions must be removed
from xrow.cc, before renaming xrow.cc to xrow.c.

Part of #2507

* Fix handling of encoded data
* Remove \n added by libyaml
* Add a test case

Follow up #128

CURLOPT_POST option without explicitly set CURLOPT_POSTFIELDS caused
libcurl to use some internal implementation of CURLOPT_READFUNCTION,
which reads body from stdin by default.

Provided test case only covers argument handling because there is no
repetable way to check reads from stdin from our test suite.

Closes #2530

Multistatement queries behaviour is undefined when they are sended
via IPROTO. There is no standard, what result must be returned
from multistatement queries.

Forbid them on a grammar level and implement special function to
split multistatement queries into an array of valid single-statement
queries for tests.

Old variant converted tuple to Lua table and then encoded to yaml
New variant encodes tuple to yaml directly.

Results of benchmarking with:

	old: 1m27.555s
	new: 0m48.738s
	Acceleration 44%

Closes #128

No semantic changes.

Needed for #128

This code was added by me, it is not covered by lua-yaml
copyrights and can be moved to src/.

See cd0d6f25 "incorrect error handling in lyaml".

Needed for #128

* Inline IS_PRINTABLE macros into check_utf8()
* Rename yaml_check_utf8() to utf8_check()
* Get rid of libyaml-private dependency for lua-yaml

Needed for #128

libsql should be STATIC.

In our terminology, page index is index of pages in a run while row
index is index of rows in a page. Rename page index to row index where
appropriate.

Tarantool should not crash if one space was truncated simultaneosly from
two fibers.

Closes #928

Follow up f1862699 ("vinyl: test vylog error handling")

Forgot to update it after adding a new errinj code - my fault :-(

Some verification spaces (q1 and q2) are not truncated before
every test round and that sometimes causes wrong results.

Fix it.

Need for #944

Check that:
 - Error writing to vylog does not break vinyl permanently.
 - An index drop/truncate/create record that was not written to vylog
   due to a write error is buffered and flushed along with the next
   write.
 - A buffered index drop/truncate/create record that hasn't been flushed
   before restart is replayed on WAL recovery.

Closes #2490

Add box.atomic(fun, arg) wrapper to execute fun(arg) in a transaction.

Closes #818

Closes #2522

* Add string.hex() method
* Add hmac.*_hex to crypto.lua
* Update crypto/digest to use string.hex()

Closes #2510

Replace the following index.info fields

  memory_used           # size of statements in memory
  size                  # size of statements on disk
  count                 # number of statements on disk and in memory
  page_count            # number of pages on disk

with

  memory
    rows                # number of statements in memory
    bytes               # size of statements in memory

  disk
    rows                # number of statements on disk
    bytes               # size of statements on disk (unpacked)
    bytes_compressed    # size of statements on disk (packed)
    pages               # number of pages on disk

  rows                  # total number of all statements
  bytes                 # total size of all statements

To achieve that, this patch introduces new classes that can be used for
accounting statements on disk and in memory, vy_stmt_disk_counter and
vy_stmt_counter, and makes vy_slice, vy_run, vy_range, and vy_index use
them instead of counting rows, bytes, and pages directly. The difference
between the two classes is that vy_stmt_counter only accounts rows and
bytes, while vy_stmt_disk_counter also includes bytes_compressed and
pages. The classes will be reused for accounting reads and writes later.

Needed for #1662

 - Delete unused vy_page_info->min_key_offset.
 - Move vy_run_info->{size,keys,page_infos} to vy_run, because
   they are not a part of run info stored in .index file.
 - Rename vy_run->page_infos to page_info.
 - Rename vy_page_info->count, vy_run->keys, and vy_slice->keys
   to row_count.
 - Update comments.

It's no use having a separate method for every kind of integer we want
to append to box info - int64_t should suit everyone.

Initialize a counter in box.space._truncate() implicitly
on CREATE TABLE.

See 353bcdc5 "Rework space truncation" for details about
TRUNCATE re-design.