psFree callback should be called even if reference counter is > 1

[rhl@…]

When I register a callback to see a given memory block freed, the current implementation of
psFree only calls my callback when the reference counter is equal to 1.

This callback is primarily used when a block is being erroneously freed twice, so the user
wants to be be notified of _all_ calls. Even in the absence of such errors, I believe that
a call to psFree should always result in the psFree callback being invoked.

[robert.desonia@…]

change checked into CVS. The callback is now always called on a decrement of
reference, i.e., a psFree.