+ ;; Figure out the argument name in ARG, which might be a
+ ;; symbol or a list with the actual argument name buried
+ ;; in it somewhere. Once we've found it, return the
+ ;; appropriate entries to add to the BVL, PUBLIC, and
+ ;; PRIVATE lists.
+ ;;
+ ;; The PATH indicates a route to take through the tree to
+ ;; find the actual argument name: it's a list of
+ ;; nonnegative integers, one for each level of structure:
+ ;; the integer indicates which element of the list at that
+ ;; level to descend into to find the argument name
+ ;; according to the usual BVL syntax. It's always
+ ;; acceptable for a level to actually be a symbol, which
+ ;; is then the argument name we were after. If we reach
+ ;; the bottom and we still have a list, then it must be a
+ ;; (PUBLIC PRIVATE) pair.
+