another problem with spinbuttons

[Paul Barton-Davis <pbd Op Net>]

since the adjustment is updated every time a "spin" is done, you get 
"value_changed" signals from the adjustment for the duration of a
spin. this is often desirable, but sometimes its not. if what happens
in the value_changed handler is "expensive" (e.g shutting down
setitimer(2) and rearming it with a new value that it 1 msec less than
the old one), such rapid changing is not very desirable.

it would be nicer to be able to say "only change the adjustment when
on button release". it would be nice, therefore, if the button in a
spin button was made accessible so that one could get a "clicked" or
"release" event from it. perhaps it is already ?

--p