message: elle.Duration: provide a means to serialize Durations as ms
  This is for backward compatibility.
diff: @@ -79,6 +79,25 @@ namespace elle
  std::ostream&
  operator << (std::ostream& s, const DurationOpt& opt);
  + template <typename Serializer, typename Duration>
  + void
  + serialize_duration_ms(Serializer& s, std::string const& name, Duration& d)
  + {
  + using milliseconds = std::chrono::milliseconds;
  + if (s.out())
  + {
  + int ms = std::chrono::duration_cast<milliseconds>(d).count();
  + s.serialize(name + "_ms", ms);
  + }
  + else
  + {
  + int ms;
  + s.serialize(name + "_ms", ms);
  + d = milliseconds(ms);
  + }
  + };
  +
  +
  #if 0
  namespace serialization
  {
  