message: fix log line format issue
diff: @@ -87,7 +87,7 @@ logger logger::stream(lockable_stream& ostr, int level_mask, bool inc_src)
  const std::string& msg,
  const char* file, int ln) {
  std::ostringstream oss;
  - oss << wampcc::local_timestamp()
  + oss << wampcc::local_timestamp() << " "
  << wampcc::thread_id() << " "
  << level_str(level) << " "
  << msg;
  