configure: disable FFmpeg-based decoders.
configure: disable FFmpeg-based decoders.

FFmpeg decoders are still available through the --enable-ffmpeg option
but are no longer maintained.

ceyusa/gstreamer-vaapi,sreerenjb/sree-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,CapOM/gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,ceyusa/gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,CapOM/gstreamer-vaapi,CapOM/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,GStreamer/gstreamer-vaapi,GStreamer/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,sreerenjb/sree-gstreamer-vaapi,sreerenjb/sree-gstreamer-vaapi