Fixed QtMultimedia core namespace compilation.

Change-Id: Ie276a7766bd26f3e49b2bc9c1a28ec96f1e3e4b0
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>

src/plugins/gstreamer/mediacapture/qgstreamerimagecapturecontrol.h

@@ -45,7 +45,8 @@
 
 #include <qcameraimagecapturecontrol.h>
 #include "qgstreamercapturesession.h"
-QT_USE_NAMESPACE
+
+QT_BEGIN_NAMESPACE
 
 class QGstreamerImageCaptureControl : public QCameraImageCaptureControl
 {
@@ -70,4 +71,6 @@ private:
     int m_lastId;
 };
 
+QT_END_NAMESPACE
+
 #endif // QGSTREAMERCAPTURECORNTROL_H