memory checking functions

[matti_karjalainen@hut.fi]

David S. Bright and Lawrence Au discussed about memory checking functions.
Thanks for the (%freebytes).

Now my question: 

Is there any way to automatically check the free Lisp heap size just after
GC. I am using an object database where my program may continue to load
objects until it is out of Lisp heap. I would like to define a function to
be called from Lisp after GC so that my program may purge some objects if
Lisp heap is too low.

Matti Karjalainen
Helsinki University of Technology
Finland