message: put std::endl onto stream object, to trigger stream sync
diff: @@ -93,11 +93,12 @@ logger logger::stream(lockable_stream& ostr, int level_mask, bool inc_src)
  << msg;
  if (inc_src && file)
  oss << " (" << file << ":" << ln << ") ";
  - oss << std::endl;
  ostr.lock();
  try {
  - ostr.stream() << oss.str();
  + // std:endl should act directly on the stream object, so that stream can
  + // detect it and trigger stream sync.
  + ostr.stream() << oss.str() << std::endl;
  } catch (...) {}
  ostr.unlock();
  };
  