FFmpeg Upstream Rebase July 1 2020

Rebased upstream and collapsed all GIPHY commits. Most fixes have made it to FFmpeg mainline.

gif transparency fixes pt 2

this fixes the disposal method issue as well

Upstream Merge 03/14/19

Brought in a lot of upstream changes that include Bjorn's and more fixes to GIF codec and format.

Test Upstream Changes 03/14

upstream-merge-03-14-19-rc1

Merge remote-tracking branch 'upstream/master'

Upstream Merge 04/02/19

Merge pull request #2 from Giphy/upstream-merge-03-14-19-v2

Upstream merge 03 14 19 v2

Transparency Fix RC 1

cr-1266

CR-1266: Fix infinite loop bug on transparent optimization

FFmpeg 4.x

brought in upstream again

FFmpeg 4.0

merged FFmpeg 4.0 upstream changes

JPEG fix, etc.

Brings in change to solve JPEG decoding issues. Fingers crossed!

GIF Disposal Fix

giphy-1.0.2

Merge remote-tracking branch 'upstream/master'