Add ability to remove dependancy on the QtNetwork module

The QWSSocket class subclasses QTcpSocket by default, hence the reason for linking against the QtNetwork module. However, Brisbane added the ability to remove this dependancy by removing QT_NO_SXE from the qconfig.h file. In this case, the base class falls back to QUnixSocket which is a private class in QtGui.

Although we can't change this default without breaking BC, it would be nice, if we cleaned this up a bit so customers could add a define at configure time to fall back to QUnixSocket instead and avoid the dependancy on QtNetwork.