MFH: r526491

games/anki: Update to 2.1.16

• Backport two patches from upstream that fix the argument handling with multimedia/mpv since r520597.

• Also slightly change the MASTER_SITES as upstream distribute tarballs for newer versions only via GitHub.

Although there are already some newer releases available use the 2.1.16
release for a while. It's mainly because the build process has changed a
lot since the 2.1.17 release and still needs to be investigated a little
more closely.

Changelog:

https://apps.ankiweb.net/docs/changes.html#changes-in-2.1.16

Approved by: ports-secteam bugfix blanket