[mythtv] ffmpeg pull requests

[Scott Theisen]

New plan:
1. https://github.com/MythTV/mythtv/pull/416 ffmpeg cleanup which includes:
1.1a. https://github.com/MythTV/mythtv/pull/568 stylistic change
1.1b. https://github.com/MythTV/mythtv/pull/565 lavc/utils-mythtv.c
1.1c. https://github.com/MythTV/mythtv/pull/576 Miscellaneous MythTV 
changes
1.1z. https://github.com/MythTV/mythtv/pull/557 ByteReader

1.2. https://github.com/MythTV/mythtv/pull/577 BitReader (depends on 1z 
only)
1.2a. test bitreader independently? I'm not sure how.

1.3. ffmpeg-cleanup also includes av_disposition which is the first 
commit inhttps://github.com/MythTV/FFmpeg/pull/4 and the second 
mpegts-mythtv.h harmonize commit (in reverse order for some unknown reason)

2. test new FFmpeg cleanup

3. merge FFmpeg cleanup into master

4. apply the harmonize commits to a MythTV branch (I'll rebase 
https://github.com/MythTV/mythtv/pull/524 once the cleanup commits are 
merged.)

5. Test the harmonize branch, especially with DSMCC/MHEG, which I 
couldn't test.

6. apply the harmonize commits to FFmpeg 
https://github.com/MythTV/FFmpeg/pull/4

7. Apply FFmpeg commits until version 5.0

8.  copy FFmpeg 5.0 into mythtv

9. test FFmpeg 5.0

Scott