free opt_names at the end of main() based on a patch by Limin Wang

Originally committed as revision 8268 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -3810,6 +3810,7 @@ int main(int argc, char **argv)
 
     av_free(intra_matrix);
     av_free(inter_matrix);
+    av_free(opt_names);
 
 #ifdef CONFIG_POWERPC_PERF
     extern void powerpc_display_perf_report(void);