It fixes a bad bug that crashes the server in certain conditions
as shown in issue #2210.

Thanks to @badboy for the help in checking the build after the fix.

This syncs lua-cmsgpack with the mattsta/lua-cmsgpack upstream.

Fixes #2161

Main reasons for upgrade:
  - Remove a warning when building Redis
  - Add multi pack/unpack
  - Improve memory usage and use Lua allocator properly
  - Fix some edge case encoding/decoding bugs