QGst/discoverer: fix inheritance of DiscovererInfo & DiscovererStreamInfo
QGst/discoverer: fix inheritance of DiscovererInfo & DiscovererStreamInfo

The real superclass is GObject, not GstObject.

dejunk/gstreamer,iperry/qt-gstreamer,GStreamer/qt-gstreamer,GStreamer/qt-gstreamer,GStreamer/qt-gstreamer,detrout/qt-gstreamer,knuesel/qt-gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,nasserGanjali/QtGStreamer,iperry/qt-gstreamer,dejunk/gstreamer,knuesel/qt-gstreamer,detrout/qt-gstreamer,knuesel/qt-gstreamer,nasserGanjali/QtGStreamer,nasserGanjali/QtGStreamer,dejunk/gstreamer,iperry/qt-gstreamer,tswindell/qt-gstreamer,tswindell/qt-gstreamer,detrout/qt-gstreamer,tswindell/qt-gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer