(holiday-list, calendar-check-holidays, calendar-mark-holidays)

(holiday-list, calendar-check-holidays, calendar-mark-holidays)
(calendar-list-holidays, holiday-filter-visible-calendar):
New names to clean up namespace.
(filter-visible-calendar-holidays, list-calendar-holidays)
(mark-calendar-holidays, check-calendar-holidays, list-holidays):
Add compatibility aliases.
(calendar-check-holidays, calendar-mark-holidays)
(calendar-holiday-list, holiday-filter-visible-calendar): Use dolist.
(holiday-sexp): Replace append with list.
(holiday-filter-visible-calendar): Replace append with push.