[CM] s7 GC bug

[bil at ccrma.Stanford.EDU]

I haven't had time yet to look at that problem in detail,
but just to clear up one point: (gc #f) turns off the GC,
so the heap can't expand, so if more space is needed,
everything goes to hell.  Also, you can use
*rootlet-redefinition-hook* to see if globals are
being redefined.  I added these lines to glob.scm"

(set! (*s7* 'heap-size) (* 20 1024000)) ; start with a  huge heap
(set! (hook-functions *rootlet-redefinition-hook*)
       (list (lambda (hook)
               (format *stderr* "redefining ~A ~A~%"
                       (hook 'name) (hook 'value)))))

and glob ran to completion with these warnings (among others):

redefining lambda #<expansion* (pspec :rest body)>
redefining macro #<expansion* (pspec :rest body)>

I think it is lambda that is actually triggering the
unbound symbol error and the free-cell error.