RELEASE_NOTES: Based on the version from 4.3

Name suggested by jb and Reto

Signed-off-by: Michael Niedermayer <[email protected]>

lavfi/buffersink: cast to uint64_t before shifting.

Fix CID 1466666.

FFmpeg 4.3.1 release

FFmpeg 4.2.4 release

FFmpeg 2.8.17

FFmpeg 4.1.6 release

FFmpeg 4.0.6 release

FFmpeg release 3.4.8

FFmpeg 3.2.15 release

Main development, master branch after release/4.3 branched off