Method stateless_reference_hash

include/sol/reference.hpp:878–879

		using is_transparent = std::true_type;

		stateless_reference_hash(lua_State* L_) noexcept : stateless_stack_reference_hash(L_) {
		}

		result_type operator()(const stateless_reference& lhs) const noexcept {
			std::hash<const void*> h;