ensure important docs are built by the automated publisher

this workaround makes sure that qdoc can find the \class
and \namespace declarations.

Change-Id: I950e6fbc10064f438d7f282ff20783acdf20de27
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/multimedia/qtmedianamespace.h

@@ -54,6 +54,9 @@ QT_BEGIN_NAMESPACE
 
 QT_MODULE(Multimedia)
 
+// Class forward declaration required for QDoc bug
+class QString;
+
 #define Q_DECLARE_METADATA(key) Q_MULTIMEDIA_EXPORT extern const QString key
 
 namespace QtMultimedia