Re-order so that functions are defined before use.

Re-order so that functions are defined before use.
(displayed-month, displayed-year): Move declarations where needed.
(chinese-calendar-time-zone, calendar-goto-chinese-date): Doc fix.
(chinese-calendar-celestial-stem, chinese-calendar-terrestrial-branch):
Add doc strings.
(chinese-year-cache): Recenter on 2010.  Doc fix.
(chinese-year, number-chinese-months, calendar-absolute-from-chinese):
Doc fix.  Simplify.
(chinese-year-cache-init): New function.
(compute-chinese-year, holiday-chinese-new-year)
(calendar-chinese-date-string, calendar-goto-chinese-date)
(make-chinese-month-assoc-list): Use cadr, nth.
(chinese-months): Remove un-needed let.