Silence "assdec.c:146: warning: passing argument 4 of ‘qsort’ from incompatible pointer type"

The alternative (schoolbook) solution is less readable.

Originally committed as revision 17230 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/assdec.c

@@ -143,7 +143,7 @@ static int read_header(AVFormatContext *s, AVFormatParameters *ap)
         p++;
     }
 
-    qsort(ass->event, ass->event_count, sizeof(*ass->event), event_cmp);
+    qsort(ass->event, ass->event_count, sizeof(*ass->event), (void*)event_cmp);
 
     return 0;