DirectX: don't set the cooperative level on WinRT

WinRT apps are not cooperative :)

modules/audio_output/directx.c

@@ -612,12 +612,14 @@ static int InitDirectSound( audio_output_t *p_aout )
      * sound without any video, and so what window handle should we use ???
      * The hack for now is to use the Desktop window handle - it seems to be
      * working */
+#ifndef VLC_WINSTORE_APP
     if( IDirectSound_SetCooperativeLevel( p_aout->sys->p_dsobject,
                                           GetDesktopWindow(),
                                           DSSCL_EXCLUSIVE) )
     {
         msg_Warn( p_aout, "cannot set direct sound cooperative level" );
     }
+#endif
     return VLC_SUCCESS;
 
  error: