add /etc/alsa/conf.d by default
I'm setting up a new machine - noticed while reading /usr/share/alsa/alsa.conf that /etc/alsa/conf.d is referenced, which doesn't exist.
However, /etc/conf.d/alsa does exist, though, and contains comments referring to saving/restoring mixer settings - maybe we should replace the reference to /etc/alsa/conf.d with a reference to /etc/conf.d/alsa?