Because ffmpeg checks out libswscale via an svn:externals, checking out an old ffmpeg does not check out a correspond...

Original commit message from CVS:
2008-04-14  Andy Wingo  <wingo@pobox.com>

* autogen.sh:
* ffmpegrev (FFMPEG_EXTERNALS_UPDATE): Because ffmpeg checks out
libswscale via an svn:externals, checking out an old ffmpeg does
not check out a corresponding libswscale. Keep the swscale
checkout manually synchronized, then. Update this when you update
FFMPEG_REVISION.