Method copy_assign

Libs/sol/sol.hpp:9169–9175

		}

		lua_State* copy_assign(lua_State* L, lua_State* rL, const stateless_reference& r) {
			if (valid(L)) {
				deref(L);
			}
			ref = r.copy(L);
			return rL;
		}

		lua_State* move_assign(lua_State* L, lua_State* rL, stateless_reference&& r) {
			if (valid(L)) {