Add prefix set support
Unquote LHS of a [[ ]] comparison in acid_set_is_empty
Add acid_set_is_singleton
Read all lines of a set string in acid_set_to_?arr
Add acid_set_uniq
Remove acid_set_has_* as unnecessary and unused ATM
Add acid_set_is_subset
Handle empty sets in acid_set_to_aarr
Handle empty arrays in acid_set_from_iarr
Only allow union of exact sets

Accept exact sets only for acid_set_union arguments as the union of an
exact and glob set is not necessarily an exact set and implementing
proper handling of this is too difficult and unnecessary.
Escape tags as associative array keys

Double '*' and '@' in set tags when using them as associative array
keys, as those characters alone are not valid keys. Convert some
set-manipulating functions from using associative to using indexed
arrays to avoid unnecessary overhead. Update other functions to account
for escaping.
Add acid_set_intersect(s)
Add acid_set_hit and acid_set_miss
Remove acid_set_(is_any|are_all) as unused ATM