ext/dv/gstdvdec.c: remove unneeded comment from dvdec (related to DV 4CC codes in AVI files) moved them in gstreamer/...

Original commit message from CVS:
* ext/dv/gstdvdec.c:
remove unneeded comment from dvdec
(related to DV 4CC codes in AVI files)
moved them in gstreamer/docs/random/mimetypes
* gst/asfdemux/gstasfdemux.c:
(gst_asf_demux_process_ext_content_desc):
don't send text tags if they are empty
fix mem leak on error path
* gst/ffmpegcolorspace/avcodec.h:
* gst/ffmpegcolorspace/gstffmpegcodecmap.c:
(gst_ffmpeg_pixfmt_to_caps), (gst_ffmpeg_caps_to_pixfmt),
(gst_ffmpegcsp_avpicture_fill):
* gst/ffmpegcolorspace/imgconvert.c: (img_get_alpha_info):
* gst/ffmpegcolorspace/imgconvert_template.h:
adds BGR32 and BGRA32 to ffmpegcolorspace
(still bad colors, fixing it on next commit)
helps with dvdec outputing BGR32