QGuiApplication does not send out ApplicationPaletteChange event

With the new QGuiApplication class in Qt5 it is impossible to receive QEvent::ApplicationPaletteChange events in event filters.

Looking at the code in qguiapplication.cpp (QGuiApplication::setPalette), this seems just not implemented. However, QGuiApplication should show the same behavior as QApplication::setPalette(..) when calling QGuiApplication::setPalette(..).