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

Start network port listener only after recovering all existing at
the start xlogs.

box.cfg{} should not complain if an immutable parameter is passed again
unchanged

Add exception methods to plain C.
Add an error factory to raise exceptions from plain C.

E.g. `-128` is packed as `d1ff80` instead of `d080`.

Conflicts:
	third_party/libev/ev.c

Requested by customer.

External unwind code doesn't exists for non-x86 platforms.
Allow LuaJIT to be compiled somehow.

https://github.com/rtsisyk/msgpuck/issues/2