LuaJIT submodule is bumped to introduce the following changes:
* sysprof: change C configuration API
* sysprof: enrich symtab on a new trace or a proto
* sysprof: fix SYSPROF_HANDLER_STACK_DEPTH
* sysprof: make internal API functions static
* sysprof: add LUAJIT_DISABLE_SYSPROF to Makefile
* symtab: check the _GNU_SOURCE definition

Within this changeset Tarantool-specific backtrace handler is introduced
and set to be used by sysprof machinery.

Besides, all new public Lua C API introduced within this changeset is
added to extra/exports.

Follows up #781

NO_DOC=LuaJIT submodule bump
NO_TEST=LuaJIT submodule bump
NO_CHANGELOG=LuaJIT submodule bump