Provide access to iproto sync via session.sync() binding.

The value is valid only at start of a Lua call before the first yield,
after which it may be replaced with a sync from another request
running on the same session.

+ Check Lua types for uint/decode for msgpack(ffi)/json/yaml tests

Include all neede variables to tarantool.h

tarantool.h is an external header (perhaps), so not available with
plain #include ""

Conflicts:
	CMakeLists.txt

Tell matras table that you're about to change a location
before actually changing it.

This patch adds `src/module.h` header file with definition of all public
API functions suitable to use in Lua/C modules for Tarantool. This header
is automatically generated from src/*.h by CMake (`make generate_module_api`)
by extracting code blocks between /** \cond public */ /* \endcond public */
Doxygen-style comments.

Definitions of functions in module.h are frozen and must not be changed by
future commits/releases. A new test case `app/module_api` is added to check
compilation, linkage and loading of Lua modules and functionality of
provided API functions.

Other changes:

 * Convert mysql and pg to use module.h and prepare to convert to .c
 * Fix includes in say.h, coeio.h
 * Rename luaL_pushnumber64 to luaL_pushuint64 and
          luaL_pushinumber64 to luaL_pushint64
 * Add LUA_API macros to public luaL_* functions (actually adds extern "C")

Add a test case.
The bug itself is fixed in the master.

Remove Engine::finish().
Encapsulate tuple reference management into Engine.

Sophia::rollbackStatement is not implemented.

long-run tests don't pass for sophia.

* Fix gh-698: duplicate-key error followed by segfault

* Add long_run test suite, which include test case from the
ticket for memtx and sophia engines.
Result files must be zero-diff

Test script also has been fixed in a number of ways:
  a) crud operation on sophia space always return nil
  b) sophia_space:len() is not monotonous
  c) update of primary key is not allowed

* Fix return of vclock_sum() as wal_writer() result, reuse
it for txn->signature

* Fixed incorrect tuple guard usage in execute_delete()

* Fixed sophia delete operation: return old_tuple as an
exception for SophiaIndex::replace(). Do not skip
wal_write() and correctly set txn->signature

* Put engine commit code after wal_write(), reuse proper
txn->signature. Engine->commit yet can throw an exception
on concurrent transaction conflict or error

* rollback sophia transaction on conflict

* add second test for gh-698; rename and disable zlong_run tests

* make rollback statement engine specific

* make txn_finish() engine specific; use it both by commit/rollback to gc

* refactor execute_delete()

* upgrade sophia submodule: efficient msgpack storage

* engine api: style fixes

Conflicts:
	src/box/index.h

Code review fixes for sysview branch.