[mythtv] Version 4.4.1 of FFmpeg ready for testing

[Peter Bennett]

I have merged version 4.4.1 of FFmpeg into the latest MythTV source 
master branch. The merged version is in branch devel/ffmpeg-resync. I 
have not merged it into the main master as yet in case there are problems.

I have run a few basic tests of playback with NVDEC, VDPAU and Standard 
(ffmpeg software) decoding. Also I tested recording/LiveTV with Ceton. 
All tests were successful.

Anybody who is interested, please build and test it to verify that all 
is well before we merge it into the main master branch.

Peter