(copy_public_confs): Handle new range-based representation of memberships.

(adjust_read): Ditto.
(insert_loc_no): Ditto.
(do_add_member): Ditto.
(do_sub_member): Ditto.
(check_membership): Ditto.
(mark_as_read): Ditto.
(do_get_membership): Ditto.
(get_unread_confs): Ditto.
(set_unread): Ditto.
(set_last_read): Ditto.
(last_text_read): New static inline function.