(Commentary): Point to calendar.el.

(Commentary): Point to calendar.el.
(calendar-holiday-list, holiday-easter-etc): Simplify by using mapcar.
(calendar-list-holidays): Return holiday-list.
(list-holidays): Use let rather than let*.  Remove un-needed locals
`d', `never'.
(calendar-check-holidays): Return result from dolist.
(holiday-float): Use a single let*.  Simplify if-and to and.
(holiday-sexp, holiday-advent, holiday-greek-orthodox-easter): Use a
single let*.