These files are from the SoundTouch library (http://www.surina.net/soundtouch/),
and are extracted from tagged version 2.3.1 of the git repository at
https://codeberg.org/soundtouch/soundtouch/.

The whole library is not used, only the relevant files are imported in the tree,
using the script `update.sh`. Some changes have been made to the files, using
the patch `moz-libsoundtouch.patch`. We also use a custom soundtouch_config.h.