set video_enc->sample_aspect_ratio to fix stream copy

patch by Wolfram Gloger  wmglo _at_ dent.med.uni-muenchen _dot_ de

Originally committed as revision 15457 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -2972,6 +2972,7 @@ static void new_video_stream(AVFormatContext *oc)
     if (video_stream_copy) {
         st->stream_copy = 1;
         video_enc->codec_type = CODEC_TYPE_VIDEO;
+        video_enc->sample_aspect_ratio =
         st->sample_aspect_ratio = av_d2q(frame_aspect_ratio*frame_height/frame_width, 255);
     } else {
         const char *p;