Move many autoloads to separate file, cal-loaddefs.el.

Move many autoloads to separate file, cal-loaddefs.el.
Move defcustoms to start and re-order.
(calendar-month-name-array, calendar-starred-day): No need to declare
for compiler.
(cal-loaddefs): Require it.
(appt, chinese-calendar, calendar-tex): Move custom groups to the
appropriate file.
(diary-entry-marker, calendar-today-marker, calendar-holiday-marker):
Reverse logic.
(diary-face, diary-file-name-prefix-function, diary-include-string)
(diary-glob-file-regexp-prefix, diary-face-attrs)
(diary-file-name-prefix, sexp-diary-entry-symbol)
(print-diary-entries-hook, list-diary-entries-hook)
(nongregorian-diary-listing-hook, mark-diary-entries-hook)
(nongregorian-diary-marking-hook, diary-list-include-blanks):
Move to diary-lib.
(all-christian-calendar-holidays, all-islamic-calendar-holidays)
(all-bahai-calendar-holidays): Doc fix.
(calendar-mark-ring): Add doc-string.
(calendar-starred-day): Defvar it.
(calendar-mode): Make calendar-starred-day local.
(calendar-star-date): No need to make calendar-starred-day local.