[CM] snd: x-zoom and :track-and-return cursor

[anders.vinjar at bek.no]

Hi Bill, thanks for fast response.  The zoom-focus-middle thing is
working great now.

However, the track-and-return is still buggy:

   (begin
     (set! (with-tracking-cursor) :track-and-return)
     (let ((here (cursor)))
       (play :start (cursor))
       (format #f "here: ~A there: ~A " here (cursor))))
   "here: 15885536 there: 0 "

Possibly another (related?) issue:

If i (play (cursor) :wait #f), snd plays, but the listener hangs until
some keyboard interrupt (e.g. C-t ).

Doing the same '(play (cursor)) from stdin, and then sending
'(stop-playing), snd does not stop, but continues to play until the snd
window gets active by moving the mouse over it or some such.

-anders