Issue: ALIST-NIL (Version 4)

[Jon L White <jonl@lucid.com>]

re: One possibility we discussed was to document that an "alist" is in fact a
    list of pairs, but to document that the functions ASSOC, RASSOC, ASSOC-IF,
    ASSOC-IF-NOT RASSOC-IF and RASSOC-IF-NOT will accept not only an alist but
    any list whose elements are either pairs or NIL, and that NIL elements are
    ignored. This means that the concept of "alist" is kept to the traditional
    interpretation, but that the behavior of some of the functions are
    extended.

I rather like this "way out" of the problem.

-- JonL --