Send expose event when application changes size

When the geometry of a wayland window is changed from the application
itself (with QWindow::setGeometry) there should be an expose event sent,
so that for example the scene graph renderer updates the size of the
rendered view.

Change-Id: If78710a9ff2693596c105ab32d3bdc2e39dbdb02
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>
Reviewed-by: Pier Luigi Fiorini <pierluigi.fiorini@gmail.com>
Reviewed-by: Andy Nichols <andy.nichols@digia.com>