Turn buffer local syntax variables into constants
* lisp/org.el (org-ds-keyword-length, org-deadline-regexp,
org-deadline-time-regexp, org-deadline-time-hour-regexp,
org-deadline-line-regexp, org-scheduled-regexp,
org-scheduled-time-regexp, org-scheduled-time-hour-regexp,
org-closed-time-regexp, org-keyword-time-regexp,
org-keyword-time-not-clock-regexp, org-maybe-keyword-time-regexp,
org-all-time-keywords): Turn into a defconst, no longer
buffer-local.
(org-set-regexps-and-options): No need to set anymore previous
variables.