memleak fix by (Jake Page <jake at CS dot Stanford dot EDU>)

with minor fix by me

Originally committed as revision 2014 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo.c

@@ -476,6 +476,9 @@ void MPV_common_end(MpegEncContext *s)
 {
     int i;
 
+    av_freep(&s->parse_context.buffer);
+    s->parse_context.buffer_size=0;
+
     av_freep(&s->mb_type);
     av_freep(&s->p_mv_table_base);
     av_freep(&s->b_forw_mv_table_base);