Added changeEvent calls where appropriate

Need to call into the superclass in order not to lose functionality. Was
missing in the wizard, hence the many missing occurrences.

Reviewed-by: Friedemann Kleint

src/plugins/coreplugin/mainwindow.cpp

@@ -986,6 +986,7 @@ void MainWindow::removeContextObject(IContext *context)
 
 void MainWindow::changeEvent(QEvent *e)
 {
+    QMainWindow::changeEvent(e);
     if (e->type() == QEvent::ActivationChange) {
         if (isActiveWindow()) {
             if (debugMainWindow)