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/mediaplayer/qt7playercontrol.mm

@@ -174,7 +174,7 @@ void QT7PlayerControl::setMedia(const QMediaContent &content, QIODevice *stream)
 {
     m_session->setMedia(content, stream);
 
-    emit mediaChanged(content);
+    Q_EMIT mediaChanged(content);
 }
 
 bool QT7PlayerControl::isAudioAvailable() const