[openal] OpenAL Soft 1.21.1 released!

[Chris Robinson]

An update for 1.21 is now out:

https://openal-soft.org/

This release has some fixes for capture on macOS and Android, and with
building for Windows ARM targets. There are also fixes for sound source
updates getting missed in certain situations, and for the internal
calculation precision issues causing the local source position to
erroneously pan away from the listener.

With this release, I've also started mirroring the source code on
Gitlab, for people who prefer to use that instead of GitHub:
https://gitlab.com/chriskcat/openal-soft

For the time being, issues and pull requests are still being handled
through GitHub, but I'll see about doing them through Gitlab as well,
as long as it doesn't make management too difficult or convoluted for
both.

As always, feedback, bug reports, etc, are appreciated. Thanks!