Allow to use tarantool/small library in modules.

Conflicts:
	src/fiber.h
	src/lib/small
	test/app/module_api.c
	test/app/module_api.result

Make sure we don't duplicate declarations in multiple places.

Save developers time on debugging stored procedures.
Closes #1100.

Thanks Vyacheslav Egorov for the fix in LuaJIT.

Update third_party/luajit to v2.1 as suggested by Vyacheslav Egorov.

Replace copy-pasted code by calls to LuaJIT internal API.
Remove useless memset(). Remove size argument from luaL_pushcdata().
Add comments and try to make this stuff to be more clear.

Performance boost up to 10% on cbench

Please never use lua_pushinteger for numbers >= INT32_MAX

Base class defines it with const qualifier.

If building for 32 bit x86 target pass -march=i686 option to enable
atomic instructions.  i686 is usually the default arch but sometimes an
older one is selected (depends on gcc compile time configuration).

Use vclock_sum() from WAL writer as a transaction signature.
Fix handling of transactions without the write requests.

getaddrinfo() on osx upto osx 10.8 crashes when AI_NUMERICSERV is set
and servername is either NULL or "0" ("00" works fine)

Based on the workaround in https://bugs.python.org/issue17269