QPixmap::fromImage() should detach when changing QImage format

When QPixmap::fromImage() detects an ARGB32 image with only opaque
pixels it will do a conversion where it only changes the advertised
format of the image. This conversion was lacking a check to see if it
the QImage was shared before doing so, which this patch adds.

Task-number: QTBUG-40282
Change-Id: I3acf221b76735637cef04c2104a33f87e5f09d54
Reviewed-by: Andreas Löw <andreas@code-and-web.de>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Windows: Fix assignment of margins in QPageSetupDialog.

Task-number: QTBUG-40061
Change-Id: Id5c952a7d6280f2ab7180bff01911d6cffe57034
Reviewed-by: Kai Koehne <kai.koehne@digia.com>