Change the length of the natarr array.
In the execution this resizes (to grow or shrink) the underlying Common Lisp array. The logical definition is based on resize-list:
Function:
(defun resize-nats$a (stobjs::i natarr$a) (declare (xargs :guard (natarr$ap natarr$a))) (resize-list natarr$a stobjs::i '0))