ext/ffmpeg/: Add the CODEC_FLAG_GLOBAL_HEADER to the exposed flags, and makes it...

ext/ffmpeg/: Add the CODEC_FLAG_GLOBAL_HEADER to the exposed flags, and makes it as such configurable as a property. ...

Original commit message from CVS:
Patch by: Mark Nauwelaerts <manauw at skynet dot be> and
Thomas Vander Stichele  <thomas at apestaart dot org>
* ext/ffmpeg/gstffmpegcfg.c: (gst_ffmpeg_flags_get_type):
* ext/ffmpeg/gstffmpegcodecmap.c: (gst_ffmpeg_codecid_to_caps),
(gst_ffmpeg_caps_with_codecid), (gst_ffmpeg_caps_to_codecid),
(gst_ffmpeg_get_codecid_longname):
Add the CODEC_FLAG_GLOBAL_HEADER to the exposed flags, and makes it as such
configurable as a property. Fixes #393187.