Replace deprecated CodecID and CODEC_ID_* by AVCodecID and AV_CODEC_ID_* everywhere in xbmc code.

Ok, this was boring but had to be done at some point. Some months ago FFmpeg renamed them as in $subject and used some tricks to preserve the old names until the next major version. xbmc was using some mixed style of CODEC_ID and AV_CODEC_ID in some parts of its code; since those appeared in ffmpeg-1.0 which xbmc already requires, just switch to the new name and be done.