Major changes:

 - All common logic and code from all serializes replaced by
   luaL_field/luaL_serializer functions
 - All features and methods were unified
 - cdata support added to JSON
 - ffi's .NULL added to JSON
 - .cfg{} method added to MsgPack, YAML and JSON
 - .new() method added to MsgPack and YAML
 - NaN and Inf checks ported from JSON
 - array vs map detection logic ported from JSON
 - support for __serialize hint added for table/cdata/userdata
 - _serializer_compact and _serializer_type superseded by __serialize
 - 64-bit integers encoding/decoding fixed in JSON and YAML
 - floating point encoding/decoding fixed in YAML
 - JSON was converted from submodule
 - New TAP-based tests added for MsgPack, MsgPackFFI, YAML, JSON

(so user can use 'SO_REUSEADDR' option in tcp_server)

Conflicts:
	src/lua/bsdsocket.lua
	test/box/bsdsocket.result
	test/box/bsdsocket.test

update sophia submodule.

Clear errno for UNIX socket connections as well.

Make the formatting of the test output platform-independent.

Do not align maxalloc (the limit on the amount of memory
used by the allocator), it's not necessary.

Make an effort to correctly align large (for 32 bit) prealloc
values (like, a few gigs).