in libavcodec/imgconvert.c.
Avoid to break compatility when making the functions dealing with
pixel format names in imgconvert.c use the names defined in pixdescs.
Originally committed as revision 20624 to svn://svn.ffmpeg.org/ffmpeg/trunk
This way pixdescs can be used without requiring a dependency on
libavcodec.
Originally committed as revision 20389 to svn://svn.ffmpeg.org/ffmpeg/trunk