Prepare to move some configuration settings from AudioOutput to
AudioOutputControl.

release v0.20.8

Apparently, this makes old clang versions happy ("'alignas' attribute
cannot be applied to types).

Prepare for Mac OS X support by omitting those Ubuntu-specific
commands.

.. and not update-alternatives, which requires "sudo".

We can remove those C++11 and C++14 kludges because we require GCC 4.9
now.