Fix memleak in opencv.

modules/video_filter/opencv_example.cpp

@@ -113,6 +113,7 @@ static int OpenFilter( vlc_object_t *p_this )
     char* filename = config_GetPsz( p_filter, "opencv-haarcascade-file" );
     p_filter->p_sys->p_cascade = (CvHaarClassifierCascade*)cvLoad( filename, 0, 0, 0 );
     p_filter->p_sys->p_storage = cvCreateMemStorage(0);
+    free( filename );
 
     return VLC_SUCCESS;
 }