nixpkgs

daf861a8 - ffmpeg: 3.4.6 -> 3.4.7 (security)

ffmpeg: 3.4.6 -> 3.4.7 (security) Fixes #75964 and #68560 (many CVEs). https://git.ffmpeg.org/gitweb/ffmpeg.git/blob/289a79d545e83a:/Changelog (cherry picked from commit 37e1da287483eac4a62597c73f31708389bfad19)