Make QWinRTImageEncoderControl a Q_OBJECT.

Fix lupdate warning:

qtmultimedia/src/plugins/winrt/qwinrtimageencodercontrol.cpp:60: Class 'QWinRTImageEncoderControl' lacks Q_OBJECT macro

when parsing the tr() in
QWinRTImageEncoderControl::imageCodecDescription().

Change-Id: I004c05c8cea620e30bff7a2b35b83eed01b7ed4c
Reviewed-by: Andrew Knight <andrew.knight@intopalo.com>

src/plugins/winrt/qwinrtimageencodercontrol.h

@@ -44,6 +44,7 @@ QT_BEGIN_NAMESPACE
 class QWinRTImageEncoderControlPrivate;
 class QWinRTImageEncoderControl : public QImageEncoderControl
 {
+    Q_OBJECT
 public:
     explicit QWinRTImageEncoderControl(QObject *parent = 0);