ext/ffmpeg/gstffmpegcodecmap.c: Improve debugging of codec data. realvideo caps are underspecified, use fields of alt...

Original commit message from CVS:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_caps_with_codecid):
Improve debugging of codec data.
realvideo caps are underspecified, use fields of alternative variant
before we settle this.
* ext/ffmpeg/gstffmpegdec.c: (gst_ffmpegdec_open),
(gst_ffmpegdec_video_frame):
Add more debugging of used parsers.
Setup the realvideo slices correctly before calling the decoder, fixed
realvideo in matroska.