Use the native parent's window if the widget in question does not
have one. This should be in line with Qt 4.8 using effectiveWinId().
Remove redundant code in grabMouse(QCursor).
Change-Id: Id6ab192e739221fe89f865f4d2f7a6d4671a190b
Reviewed-by: Qt Doc Bot <qt_docbot@qt-project.org>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>