When time is running out, the alarm is sounded once
every second, which is really obnoxious, IMHO. This
patch will cause it to be played only once (per game).
FYI, my particular config is to play sounds by running
esdplay, but from the code it looks like the behavior I
describe would happen with any sound config.
It's conceivable that someone might want more
flexibility, and I'd be happy to learn and play with
the dlg_prefs interface, but I thought I'd start out by
submitting something simple. It's a one line change in
LowTimeWarning() (line 191) of clock.cc.