Move QVideoWindowControl out of widgets.

There is no widget dependency in it, and this enables the QML
Video element to support video overlays later.

Change-Id: I7ebcde350f9595a9f7c319663ff745930535a8a7
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/gstreamer/qgstreamervideowindow.h

@@ -46,6 +46,7 @@
 
 #include "qgstreamervideorendererinterface.h"
 #include <private/qgstreamerbushelper_p.h>
+#include <QtGui/qcolor.h>
 
 QT_BEGIN_NAMESPACE
 class QAbstractVideoSurface;