fixes the frame number counter for -vcodec copy patch by (mru at users dot sourceforge.net (Måns Rullgård))

Originally committed as revision 1176 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffmpeg.c

@@ -1292,6 +1292,7 @@ static int av_encode(AVFormatContext **output_files,
                         /* force the input stream PTS */
                         av_write_frame(os, ost->index, data_buf, data_size);
 			ost->st->codec.frame_number++;
+			ost->frame_number++;
                     }
                 }
             }