With this the alsa backend reports the progresses too, forgot previously.

amused implements pausing as not sending audio at all until resuming, i.e. by doing an underrun. ALSA is more strict than sndio, by default at least, and so we need to call snd_pcm_recover() before we can play again.

used @openbsd.org initially by mistake and got copied around in most files. Since this has nothing to do officially with the OpenBSD project, use my own email address.

Cm on|off renders the pipe in bold too, use Cm on Ns | Ns Cm off to disambiguate.

snd_pcm_writei works in terms of audio frames, not buffer (bytes) length like snd_write does, so account for that. To do so, prepare a `bpf' (bytes per frame) multiplier in the configure stage and use it to convert back and forward between the buffer length and the number of frames. While here, also use snd_pcm_avail_update() to know how many frames may be written.