Provide forward/back/home navigation for QStackedWidget

I have reimplemented forward/back functionality for QStackedWidget (Qt4) and QWidgetStack (Qt3) several times. It's fairly easy but non-trivial because of the various corner cases.

It would be great if it QStackedWidget had forward() and back() slots as well as forwardAvailable(bool) and backAvailable(bool) signals so I could hook up a pair of forward/back buttons to it directly without having to track my own navigation. Also, the ability to set the home widget would be good too, and a slot called home().