Function is_main_thread

extlibs/sol3/include/sol/sol.hpp:10041–10045

		}

		inline bool is_main_thread(lua_State* L) {
			int ismainthread = lua_pushthread(L);
			lua_pop(L, 1);
			return ismainthread == 1;
		}

		inline void coroutine_create_guard(lua_State* L) {
			if (is_main_thread(L)) {