Original commit message from CVS:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_codecid_to_caps),
(gst_ffmpeg_formatid_get_codecids),
(gst_ffmpeg_get_codecid_longname):
* ext/ffmpeg/gstffmpegdemux.c: (gst_ffmpegdemux_loop),
(gst_ffmpegdemux_register):
* ext/ffmpeg/gstffmpegmux.c: (gst_ffmpegmux_collected),
(gst_ffmpegmux_register):
Add GIF (animations and single images) decoding and encoding support.
Fixes #503249.