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/qt7playermetadata.mm

@@ -254,7 +254,7 @@ void QT7PlayerMetaDataControl::updateTags()
     }
 
     if (!wasEmpty || !m_tags.isEmpty())
-        emit metaDataChanged();
+        Q_EMIT metaDataChanged();
 }
 
 #include "moc_qt7playermetadata.cpp"