Support logging to syslog

Simply set the logfile path to "syslog" and murmur will log to syslog.

This should be stable, it has approximately 4 user-months of testing.
With the move of syslog.h, I'd prefer if this variable was moved down below the other static vars (bVerbose, detach).
Please just add a `#ifdef Q_OS_UNIX` section with `logToSyslog` below the `#endif` fo QT_NO_DEBUG.