Debugger: Accepts port range as arguments

Allow a port range to pass on command line, and try to listen on any of the
ports in the range. (Re)using the ',' separator allows for backwards compatibility,
that is, also Qt 4 will accept a -qmljsdebugger=port:1000,1010 argument, but
will only try to listen on port 1000.

Change-Id: Ic03fe20e4aee9ecdea86651f46f1df5cb19bd75c
Reviewed-by: Kai Koehne <kai.koehne@digia.com>