FindLua50

Locate Lua library.

This module defines:

LUA50_FOUND, if false, do not try to link to Lua
LUA_LIBRARIES, both lua and lualib
LUA_INCLUDE_DIR, where to find lua.h and lualib.h (and probably lauxlib.h)

Note that the expected include convention is:

#include "lua.h"

and not:

#include <lua/lua.h>

This is because, the lua location is not standardized and may exist in locations other than lua/