ext/ffmpeg/gstffmpegcodecmap.c: WMV extradata (make #152798 work). J-frames are only...

ext/ffmpeg/gstffmpegcodecmap.c: WMV extradata (make #152798 work). J-frames are only available in the bitstream if th...

Original commit message from CVS:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_codecid_to_caps),
(gst_ffmpeg_caps_with_codecid):
WMV extradata (make #152798 work). J-frames are only available
in the bitstream if the J-frame bit has been set in the extradata.
If not (or if extradata is not provided), the movie won't play.
* ext/ffmpeg/gstffmpegdec.c: (gst_ffmpegdec_close),
(gst_ffmpegdec_connect), (gst_ffmpegdec_chain):
Only close ffmpeg if privdata was allocated (else it segfaults).
Autodetect encoding bugs and workaround it. Don't copy data if
decoding failed.
* ext/ffmpeg/gstffmpegdemux.c: (gst_ffmpegdemux_loop):
Use read_frame() instead of read_packet() which is obsolete.