Updating JIT

HolyLib has a luajit module that updates Garry's mod LuaJIT version to a newer one.
In addition, it also restores debug.upvaluejoin, debug.upvalueid, debug.setupvalue, debug.setlocal.
It also exposes lua's original require function under jit.require allowing you to require things like ffi and jit.profiler.
by default string.buffer and ffi are already loaded.

Enabling the module

1. Add -holylib_enable_luajit 1 to the server startup arguments
   
2. Restart the server
   
3. Verify using print(jit.version) that it updated. (It should print something like LuaJIT 2.1.1697887905)