message: use stdout as output stream if logstream is not provided
diff: @@ -1281,6 +1281,10 @@ void TACSIntegrator::setPrintLevel( int _print_level,
  // Open a new file for logstream
  if (mpiRank == 0){
  logfp = fopen(logfilename, "w");
  + // Use stdout as output stream if the filename is empty
  + if (!logfp){
  + logfp = stdout;
  + }
  }
  }
  }
  