Fixed compile of quicktime plugin

This code was including the qmacdefines_mac.h header from QtWidgets,
which has recently been removed.  Using the header is no longer
necessary.

Note that the qmacdefines_mac.h contained a workaround for some mac
system headers declaring variables named `slots'.  Replace that
workaround with the standard no_keywords method.

Change-Id: Icd47a562d64953692e50a9fea8bb4a9c8424375c
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/qt7/qt7videooutput.h

@@ -50,9 +50,6 @@
 #include <qvideorenderercontrol.h>
 #include <qmediaplayer.h>
 
-#include <QtWidgets/qmacdefines_mac.h>
-
-
 QT_BEGIN_NAMESPACE
 
 class QMediaPlaylist;