1 - Level-based logging.
    You can log messages on 1 of eight different message channels,
    DEBUG, INFO, NOTICE, WARNING, ERROR, CRITICAL, ALERT and EMERGENCY
    Each level is switchable on/off on the fly.
    Example :
       SysLog.EnableLevels(ERROR | WARNING | DEBUG);
       SysLog(ERROR) << "an error";
       SysLog(NOTICE) << "a notice";
       SysLog(DEBUG) << "a debug message";

    Here, just first and third messages are logged.

2 - SysLog global object, just needed to use SystemLog package.

3 - Streaming-like << operator.

4 - Logging can be directed to Cerr() and/or Cout() streams, to  
    system log file and/or to Upp application log file.
    Example :
       SysLog.EnableCout(true);
       SysLog.EnableCerr(false);
       SysLog.EnableSysLog(true);
       SysLog.EnableUppLog(true);

    Here log is put on both Cout() stream, System log file and Upp application log file.