QWizard/Win: Drag window on Vista with only left mouse button

The QWizard window should only be draggable using the left mouse button
on Vista.

Change-Id: Ie6ec118cbb48440c5dc6b84c4361119b1bbbd0cf
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/widgets/dialogs/qwizard_win.cpp

@@ -545,7 +545,7 @@ void QVistaHelper::mousePressEvent(QMouseEvent *event)
 {
     change = noChange;
 
-    if (wizard->windowState() & Qt::WindowMaximized) {
+    if (event->button() != Qt::LeftButton || wizard->windowState() & Qt::WindowMaximized) {
         event->ignore();
         return;
     }