This adds some missing prototypes from the BT.2020 CL as well as expands
the H444 and J444 results.

BUG=960620, libyuv:845, b/129864744

Change-Id: I8ea3959379f1bb2edb857d4eb90fb9a1f6aa4e03
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/1899093Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>