* sexp.c (sexp_iterator_next): Updated to new sexp_iterator_exit_list.

(sexp_iterator_exit_list): Return with iterator pointing to the
element after the list.
(sexp_iterator_check_type): Call sexp_iterator_next before
returning.
(sexp_iterator_check_types): Likewise.
(sexp_iterator_assoc): Rearranged calls of sexp_iterator_next.

Rev: src/nettle/sexp.c:1.7