Function as_function_reference

3rd_party/lua_sol2/include/sol.hpp:4977–4979

	template <typename Sig = function_sig<>, typename... Args>
	auto as_function_reference(Args&&... args) {
		return function_arguments<Sig, Args...>(std::forward<Args>(args)...);
	}

	template <typename T>
	struct as_table_t {