bug in GC

[GSB at MIT-ML (Glenn S. Burke)]

In case no one responded to this (if they did they didn't cc to bug-lisp),
the problem is that the arrays should be created as T type, not NIL
type;  eg, (array size t 5).
NIL types don't get marked through, so after the first gc the stuff which
was in them, if not protected by something else, is now on the freelist.
I have seen this "bug" before, and even encountered it myself;  it isn't
immediately obvious that NIL isn't just an ordinary notype array.