This fixes playback of DVB subtitles in
http://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket1065/Test1.wtv
in MPlayer.
FFplay is not affected since it assumes that the subtitles
are scaled to match the video - but this usually isn't the
case after rescaling the video and stream-copying subtitles.
Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>