Add decoder flush after seeking for RV3/4 decoders

Originally committed as revision 17030 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/rv30.c

@@ -276,5 +276,6 @@ AVCodec rv30_decoder = {
     ff_rv34_decode_end,
     ff_rv34_decode_frame,
     CODEC_CAP_DR1 | CODEC_CAP_DELAY,
+    .flush = ff_mpeg_flush,
     .long_name = NULL_IF_CONFIG_SMALL("RealVideo 3.0"),
 };

libavcodec/rv40.c

@@ -654,5 +654,6 @@ AVCodec rv40_decoder = {
     ff_rv34_decode_end,
     ff_rv34_decode_frame,
     CODEC_CAP_DR1 | CODEC_CAP_DELAY,
+    .flush = ff_mpeg_flush,
     .long_name = NULL_IF_CONFIG_SMALL("RealVideo 4.0"),
 };