ext/ffmpeg/: Do some more random property setting. Fix for if there's less than ffmpeg-default-buffersize (32kB) data...

Original commit message from CVS:
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_codecid_to_caps),
(gst_ffmpeg_caps_to_codecid):
* ext/ffmpeg/gstffmpegprotocol.c: (gst_ffmpegdata_read):
Do some more random property setting. Fix for if there's less than
ffmpeg-default-buffersize (32kB) data in a file _and_ there's an
event pending. Partially fixes #142320.