Merge commit 'b14086ca'

* commit 'b14086ca':
  mkv: Correctly report the latest packet had been flushed
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskaenc.c

@@ -1899,7 +1899,7 @@ static int mkv_write_flush_packet(AVFormatContext *s, AVPacket *pkt)
                 mkv_flush_dynbuf(s);
             avio_flush(s->pb);
         }
-        return 0;
+        return 1;
     }
     return mkv_write_packet(s, pkt);
 }