[openal] OpenAL Soft 1.21.0 released!

[Chris Robinson]

A new version has been tagged and uploaded:

https://openal-soft.org/

Notable features in this release include the AL_SOFT_effect_target,
AL_SOFT_events, and ALC_SOFT_loopback_bformat extensions, a lock-free
real-time-safe mixer, improved memory use for mixing voices, improved
spatialization quality for quad and 7.1 output, general quality
improvements with HRTF and UHJ output, reintroduction of the modulation
stage in reverb, support for surround sound with the SoundIO backend,
along with a smattering of bug fixes. On Linux, real-time priority is
now used by default on certain backends, for improved stability against
skips and dropouts.

This release also sees initial work on new features, like an Oboe
backend for Android, convolution reverb, and a callback-based buffer
source.

There's also been a fair amount of cleanup toward separating the OpenAL
API from the core mixer, so that the same code base can be used to
implement other APIs. This isn't fully done yet, but it's getting
ever-closer.

If you encounter any issues or have any questions, please ask. Either
here through email, on the Github issue tracker (at the Github repo
<https://github.com/kcat/openal-soft>), or on IRC (#openal at
irc.freenode.org). Thanks!