Use existing virtual dispatch in _say funcptr to remove branching on
logger_type in runtime.

In context of #2795

Create a different type of logger for boot mode.

In context of #2795

This patch is pure refactoring. No functional changes intended.

Needed for #2795

If EOF is reached, recover_remaining_wals() closes recovery->cursor.
The next time it is called, it looks up the next xlog to scan with
vclockset_match(), but the latter will return vclock of the last
scanned xlog unless a new xlog has appeared since the last call.
As a result, the last xlog is scanned three times during recovery:
by recover_follow_local(), hot_standby_f(), and recovery_finalize().
To fix that, let's make recover_remaining_wals() start recovery from
recovery->vclock if it reached EOF while reading the last xlog.

Closes #2768

It isn't a good practice to access xlog_cursor::state directly, because
it may include implementation-specific states, e.g. we might want to
differentiate CLOSED_AFTER_EOF and CLOSED_WITHOUT_EOF or CLOSED and
NOT_YET_OPENED (see the next patch). Let's introduce convenient helpers
to check if a cursor is open and if it reached EOF and use them outside
xlog.c.

Needed for #2768

Allow long with field_no pass field_name for index creation
(alteration) routines.

Add new method of defining indexes:
 - parts = { {field = field_name1, type = field_type}, {field = field_name2, type = field_type}, ...}
 - parts = { {field_name1, field_type}, {field_name2, field_type}, ...}
 - parts = { {field_name1}, {field_name2}, ...}
 - parts = {field_name1, field_name2}
 - parts = {field_id, field_id}

Fix 2814

In addition to current syntax of space fileds format definition:
 - space:format({{name='field_id', type='integer'}, ...})

Add more ways to define it:
 - space:format({{'field_name', 'integer'}, ...})
 - space:format({{'field_name', type='integer'}, ...})
 - space:format({{'field_name'}, ...})
 - space:format({'field_name', ...})

Fix #2815

ucol_open() expects null-terminated string.
GCC doesn't initialize locale name buffer in RelWithDebInfo.

Fixes #2819

It is appeared that ICU v50 supports CLRD-22 when ICU v51+ supports
CLRD-23+. One of the CLRD-23 changes comparing to CLRD-22 is
local script collates before other scripts. In general that means
that having different ICU version we get different order with
non-Latin locales. The main problem is that a run that was sorted
with one version of tarantool becomes unsorted in another.

Fix tests that depends on that order and disable collation in vinyl.

Older versions of gcc do not support designated initializers.

Fixes 9a880ae6 ("Turn class Handler into struct space_vtab").

PackageCloud doesn't support Ubuntu Artful yet.

Follow up e3d97f6d

Closes #2805

The typo caused the following box.schema.user.info() failure if the user
was granted a permission to use a sequence:

  tarantool> box.schema.user.info()
  ---
  - error: 'builtin/box/schema.lua:1542: assign to undeclared variable ''seq'''
  ---

Class Handler contains only function pointers so we can easily convert
it to a C struct. This is needed to introduce internal C API to perfrom
DML requests on spaces which is required by SQL.

Needed for #2776

 - Engines should inherit struct space if they need to store engine
   specific data per space.
 - Engine::createSpace() now returns struct space instead of Handler.
 - Engines should overwrite Handler::destroy() to implement struct space
   destructor.

This is a step towards converting class Handler to struct space_vtab.

Needed for #2776

Currently, the format is stored in Handler and can be retrieved with
Handler::format(). The only reason for such a layer of indirection is
that the format should be created by an Engine method and currently it
is created by Engine::createSpace(). Let's introduce a separate method
for create a space format, Engine::createFormat(), and move the format
back to where it belongs, i.e. to struct space.

This is a step towards converting class Handler to struct space_vtab.

Needed for #2776

We gain no benefit from having them separated from corresponding
MemtxSpace::execute* methods.

This is a step towards converting class Handler to struct space_vtab.

Needed for #2776

space->handler->engine->... looks ugly. Since all Handler methods
receive space as an argument anyway, let's move engine to struct space.

This is a step towards converting class Handler to struct space_vtab.

Needed for #2776

Make new option in index part - collation - where user can pass
a name of a collation that he wants to use for comparison of the
field.

Fix #2649

Add a new space that contains collation definitions for future
index collation and more.

Add a collation cache for fast retrieving a collation object by
its name.

Needed for #2649

Introduce coll object that allows to compare strings.
Add coll_def structure and functions for its setup.
Add unit test.

Needed for #2649

Support [{field=<field_no>, type=<type>}, ...] index part format
both in box.space._index and box.schema.index.create() Lua API.

box.space_index now supports the following formats of index parts:

 1. <field_no>, <type>, <field_no>, <type>, ... -- Tarantool 1.6.0+
 2. [[<field_no>, <type>], ...] -- Tarantool 1.6.6+
 3. [{field=<field_no>, type=<type>}] -- Tarantool 1.7.6+, this patch

box.schema.upgrade() converts format #1 to #2. Format #2 is not converted
automatically to #3 yet. Let's extend box.schema.upgrade() to do that later
in order to keep upward compatibility for existing 1.7.x customers.

Lua API now supports the following formats:

1. [<field1_no>, <type1>, ,..] -- Tarantool 1.6.0+
2. [{field=<field_no>, type=<type>}] -- Tarantool 1.7.6+, this patch

In addition to format #2, [{<field_no>, type = <type>}] and
[<field_no>, <type>, may_be_added_in_the_future=xxx}] shortcut is supported.
box.schema.space.create() automatically converts format #1 to #2,
therefor all new indexes will have the new format.

Closes #2802

By some philosophic reasons it was decided to name functions
that deal with old format by name with a suffix - version of
tarantool when the format was initially introduced instead of
last version when this format was used.

Change type of 'map' argument to const char ** and return in it
the end of parsed msgpack map.

Move opt_def functions from alter.cc to opt_def.c.
Make no logical changes.

Headers duplicates are written in string separated with comma
Except special headers described in:
https://nodejs.org/api/http.html#http_message_headers

Relates to #2658

Fixes #2658

In a case of collision of field and method names, the field name have
higher priority.

Closes #1014

Aliases will allow to call tuple methods, when tuple has fields with
same names as methods. In such a case a field name has higher
priority and the tuple method with the same name becomes inaccessible
via tuple:...() API.

Needed for #1014

* Add package.search function
* Fix failing tests after patch for new loaders

Closes #2797