Default directory on Windows is now %LOCALAPPDATA% (usually <userdir>/Appdata/Local).
Better user feedback on commandline options and on missing or faulty DHTservers file.
Now continuing on missing/empty DHTservers.
Capitalization of gtk or winforms on --gui doesn't matter any longer.
If user requests an unknown gui, it's first tried as given, then all uppercase.

Mutex got a few more locks and more descriptive states.