[mythtv] FFmpeg resync

[Jean-Yves Avenard]

Hello there.

A new branch was created earlier this week: devel/resync-stable10

It's a resync of our ffmpeg copy which is now following ffmeg stable 1.0 branch.
Hopefully this will allow better backport of bug fixes as they are
added to the ffmpeg stable branch.

This should also allow to resync with ffmpeg during point release
(e.g. 0.27.0, 0.27.1 etc) rather than only during major new release.

The branch devel/resync-stable10 is now fully functional, I would
appreciate if some of you could give it a try.

The plan is to merge this branch back into master on Monday

Regards
Jean-Yves