Recognize true lists of messages.
(msg-listp x) → std::bool
This is an ordinary std::deflist. It is
"strict" in that it requires
Function:
(defun msg-listp (x) (declare (xargs :guard t)) (let ((__function__ 'msg-listp)) (declare (ignorable __function__)) (if (consp x) (and (msgp (car x)) (msg-listp (cdr x))) (null x))))