There was a little mess in exports file regarding LuaJIT symbols to be
visible from Tarantool binary, so some functions (e.g. <lua_tonumberx>
and <lua_tointegerx>) were hidden unintentionally. As a result of the
patch almost all public LuaJIT symbols are exported from Tarantool
binary; there are still several functions reasonably hidden (you can
find the rationale around the corresponding cases in the test file).

Closes #3680

@TarantoolBot document
Title: clean up LuaJIT exported functions

The list of the LuaJIT-related functions being exported (i.e. public)
from Tarantool should be updated. The actual list of the exported
symbols can be found within changeset (either extra/exports file or
related Lua test chunk).