ext/ffmpeg/: FFMpeg now provides proper long_name for AVCodec, remove our internal mapping and directly use upstream ...

Original commit message from CVS:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_codecid_to_caps),
(gst_ffmpeg_get_codecid_longname):
* ext/ffmpeg/gstffmpegdec.c: (gst_ffmpegdec_base_init),
(gst_ffmpegdec_register):
* ext/ffmpeg/gstffmpegenc.c: (gst_ffmpegenc_base_init),
(gst_ffmpegenc_register):
* ext/ffmpeg/gstffmpegmux.c: (gst_ffmpegmux_register):
FFMpeg now provides proper long_name for AVCodec, remove our
internal mapping and directly use upstream naming.
Improve debugging messages.
Remove g_warning() which isn't really needed.