(abitset_reverse_list, ebitset_reverse_list):

(abitset_reverse_list, ebitset_reverse_list):
Do not assume that bitset_windex is the same width as unsigned.
(abitset_unused_clear): Do not assume that bitset_word is the same
width as int.
(abitset_op1): Use -1, not ~0, as memset arg (for portability to one's
complement hosts!).