Replace luaL_reg with luaL_Reg as recent LuaJIT dropped the Lua 5.0 compat (#5541)

We are bundling Lua5.1 which has same macro

src/script/lua_api/l_settings.h

@@ -28,7 +28,7 @@ class LuaSettings : public ModApiBase
 {
 private:
 	static const char className[];
-	static const luaL_reg methods[];
+	static const luaL_Reg methods[];
 
 	// garbage collector
 	static int gc_object(lua_State *L);