Fixed memory lean in QImageVideoBuffer and QMemoryVideoBuffer.
Fixed memory lean in QImageVideoBuffer and QMemoryVideoBuffer.

QAbstractVideoBufferPrivate was intended to have virtual
desctructor,
otherwise subclasses are not deleted properly.

Reviewed-by: Andrew den Exter

qtproject/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,KDE/android-qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,KDE/android-qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,KDE/android-qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,tmcguire/qt-mobility,kaltsi/qt-mobility,enthought/qt-mobility,enthought/qt-mobility,KDE/android-qt-mobility,qtproject/qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,tmcguire/qt-mobility,enthought/qt-mobility,tmcguire/qt-mobility,qtproject/qt-mobility