Change the length of the bitarr 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-bits$a (stobjs::i bitarr$a) (declare (xargs :guard (bitarr$ap bitarr$a))) (resize-list bitarr$a stobjs::i '0))