message: elle.log: obey to ELLE_LOG_TIME etc.
  We should rather use ELLE_LOG_TARGETS, but at least for a while,
  ensure some backward compat.
diff: @@ -153,9 +153,12 @@ namespace elle
  auto res = make_one_logger_impl(dest, level, args);
  if (auto l = get_text_logger(res))
  {
  - l->enable_time(get(args, "time"));
  - l->time_universal(get(args, "universal"));
  - l->time_microsec(get(args, "microsec"));
  + l->enable_time(get(args, "time",
  + os::getenv("ELLE_LOG_TIME", false)));
  + l->time_universal(get(args, "universal",
  + os::getenv("ELLE_LOG_TIME_UNIVERSAL", false)));
  + l->time_microsec(get(args, "microsec",
  + os::getenv("ELLE_LOG_TIME_MICROSEC", false)));
  }
  if (!args.empty())
  err<std::invalid_argument>("unused logger arguments: %s", args);
  