Major cleanup of the timerX_{acquire,release} stuff. In particular,

Major cleanup of the timerX_{acquire,release} stuff.  In particular,
make it more intelligible, improve the partially bogus locking, and
allow for a ``quick re-acquiration'' from a pending release of timer 0
that happened ``recently'', so it was not processed yet by clkintr().
This latter modification now finally allows to play XBoing over
pcaudio without losing sounds or getting complaints. ;-)  (XBoing
opens/writes/closes the sound device all over the day.)

Correct locking for sysbeep().

Extensively (:-) reviewed by:	bde