[Tarantool-patches] [PATCH 2.X v4 0/4] module api: extend for external merger Lua module

[Alexander Turenko]

The patchset looks good to me in general, however I agree with Vlad that
it would be good to polish it if we would not have so tight timeline.

I made several changes before pushing:

- 'module api: box_ibuf_* wrappers' is applied first (we need it to use
  <box_ibuf_t> for luaT_toibuf() later).
- Use <box_ibuf_t> in luaT_toibuf(). And so moved the box/ibuf.h header
  before lua/utils.h in the list of the API headers.
- Marked the last commit as 'Closes #5384' instead of 'Part of #5384'.
- Moved the luaL_iscallable 1.10 backport as first to form the proper
  chain of 'part of', 'part of', ... 'closes'.
- Found and fixed 'unused variable' warnings on module_api.c on
  RelWithDebInfo build.

Pushed to master, 2.5, 2.4 and 1.10.

WBR, Alexander Turenko.