By generating stubs using https://github.com/hpvb/dynload-wrapper we
can dynamically load libpulse and libasound on systems where it is available.
Both are still a build-time requirement but no longer a run-time dependency.
For maintenance purposes the wrappers should not need to be re-generated
unless we want to bump pulse or asound to an incompatible version. It is
unlikely we will want to do this any time soon.
cherry-pick from 09f82fa6ea
It's too hard to get compatibility between GNU and BSD sed,
so let's just use perl oneliners.
And improve it to also remove trailing tabs, not just spaces.
(cherry picked from commit c71e189efd)
Removes AppVeyor and all Travis jobs but the iOS one, which hasn't been ported
to GitHub Actions yet (should be done soon).
Backports new style scripts from `master` branch too to do the same checks.
