Method serialize

test/serialization/test_traits.cpp:30–32

  MinimalSerializable() = default;
  MinimalSerializable(::std::mt19937_64& gen) : v(gen()) {}
  void serialize(CodedOutputStream& os) const {
    SerializeTraits<int>::serialize(v, os);
  }
  bool deserialize(CodedInputStream& is) {
    return SerializeTraits<int>::deserialize(is, v);
  }