Speed up setting/getting the APPT_WARNTIME property.

* org.el (org-refresh-properties): Rename from
`org-refresh-effort-properties' and use two new parameters.
(org-agenda-prepare-buffers): Use `org-refresh-properties'.
Also refresh the 'org-appt-warntime text property.

* org-clock.el (org-clock-in): Use the renamed defun.

* org-icalendar.el (org-icalendar-print-entries): Refresh the
'org-appt-warntime property.
(org-icalendar-print-entries): Do not use `org-entry-get' to
get the "APPT_WARNTIME" property value.

* org-agenda.el (org-agenda-get-timestamps)
(org-agenda-get-sexps, org-agenda-get-deadlines)
(org-agenda-get-scheduled): Ditto.

lisp/org-agenda.el

@@ -5401,7 +5401,7 @@ Do we have a reason to ignore this TODO entry because it has a time stamp?
 	      clockp (and org-agenda-include-inactive-timestamps
 			  (or (string-match org-clock-string tmp)
 			      (string-match "]-+\\'" tmp)))
-	      warntime (org-entry-get (point) "APPT_WARNTIME")
+	      warntime (get-text-property (point) 'org-appt-warntime)
 	      donep (member todo-state org-done-keywords))
 	(if (or scheduledp deadlinep closedp clockp
 		(and donep org-agenda-skip-timestamp-if-done))
@@ -5472,7 +5472,7 @@ Do we have a reason to ignore this TODO entry because it has a time stamp?
 		category-pos (get-text-property beg 'org-category-position)
 		tags (save-excursion (org-back-to-heading t) (org-get-tags-at))
 		todo-state (org-get-todo-state)
-		warntime (org-entry-get (point) "APPT_WARNTIME")
+		warntime (get-text-property (point) 'org-appt-warntime)
 		extra nil)
 
 	  (dolist (r (if (stringp result)
@@ -5844,7 +5844,7 @@ See also the user option `org-agenda-clock-consistency-checks'."
 			   (not (= diff 0))))
 		  (setq txt nil)
 		(setq category (org-get-category)
-		      warntime (org-entry-get (point) "APPT_WARNTIME")
+		      warntime (get-text-property (point) 'org-appt-warntime)
 		      category-pos (get-text-property (point) 'org-category-position))
 		(if (not (re-search-backward "^\\*+[ \t]+" nil t))
 		    (setq txt org-agenda-no-heading-message)
@@ -5934,7 +5934,7 @@ FRACTION is what fraction of the head-warning time has passed."
 		  (match-string 1) d1 'past show-all
 		  (current-buffer) pos)
 	      diff (- d2 d1)
-	      warntime (org-entry-get (point) "APPT_WARNTIME"))
+	      warntime (get-text-property (point) 'org-appt-warntime))
 	(setq pastschedp (and todayp (< diff 0)))
 	(setq did-habit-check-p nil)
 	;; When to show a scheduled item in the calendar:

lisp/org-clock.el

@@ -35,7 +35,7 @@
 (declare-function calendar-absolute-from-iso "cal-iso" (&optional date))
 (declare-function notifications-notify "notifications" (&rest params))
 (declare-function org-pop-to-buffer-same-window "org-compat" (&optional buffer-or-name norecord label))
-(declare-function org-refresh-effort-properties "org" ())
+(declare-function org-refresh-properties "org" (dprop tprop))
 (defvar org-time-stamp-formats)
 (defvar org-ts-what)
 (defvar org-frame-title-format-backup frame-title-format)
@@ -1082,7 +1082,7 @@ time as the start time \(see `org-clock-continuously' to
 make this the default behavior.)"
   (interactive "P")
   (setq org-clock-notification-was-shown nil)
-  (org-refresh-effort-properties)
+  (org-refresh-properties org-effort-property)
   (catch 'abort
     (let ((interrupting (and (not org-clock-resolving-clocks-due-to-idleness)
 			     (org-clocking-p)))

lisp/org-icalendar.el

@@ -327,6 +327,7 @@ When COMBINE is non nil, add the category to each line."
 	tmp pri categories location summary desc uid alarm alarm-time
 	(sexp-buffer (get-buffer-create "*ical-tmp*")))
     (org-refresh-category-properties)
+    (org-refresh-properties "APPT_WARNTIME" 'org-appt-warntime)
     (save-excursion
       (goto-char (point-min))
       (while (re-search-forward re1 nil t)
@@ -357,7 +358,7 @@ When COMBINE is non nil, add the category to each line."
 			(org-id-get-create)
 		      (or (org-id-get) (org-id-new)))
 		categories (org-export-get-categories)
-		alarm-time (org-entry-get nil "APPT_WARNTIME")
+		alarm-time (get-text-property (point) 'org-appt-warntime)
 		alarm-time (if alarm-time (string-to-number alarm-time) 0)
 		alarm ""
 		deadlinep nil scheduledp nil)

lisp/org.el

@@ -8642,23 +8642,24 @@ call CMD."
 	   (put-text-property beg end 'org-category-position beg)
 	   (goto-char pos)))))))
 
-(defun org-refresh-effort-properties ()
-  "Refresh effort text properties in the buffer."
+(defun org-refresh-properties (dprop tprop)
+  "Refresh buffer text properties.
+DPROP is the drawer property and TPROP is the corresponding text
+property to set."
   (let ((case-fold-search t)
-	(inhibit-read-only t) e)
+	(inhibit-read-only t) p)
     (org-unmodified
      (save-excursion
        (save-restriction
 	 (widen)
 	 (goto-char (point-min))
-	 (put-text-property (point) (point-max) 'org-effort-timestamp (current-time))
-	 (while (re-search-forward (concat "^[ \t]*:" org-effort-property
-					   ": +\\(.*\\)[ \t]*$") nil t)
-	   (setq e (org-match-string-no-properties 1))
+	 (while (re-search-forward (concat "^[ \t]*:" dprop ": +\\(.*\\)[ \t]*$") nil t)
+	   (setq p (org-match-string-no-properties 1))
 	   (save-excursion
 	     (org-back-to-heading t)
 	     (put-text-property
-	      (point-at-bol) (point-at-eol) 'org-effort e))))))))
+	      (point-at-bol) (point-at-eol) tprop p))))))))
+
 
 ;;;; Link Stuff
 
@@ -17011,7 +17012,8 @@ When a buffer is unmodified, it is just killed.  When modified, it is saved
 	    (widen)
 	    (setq bmp (buffer-modified-p))
 	    (org-refresh-category-properties)
-	    (org-refresh-effort-properties)
+	    (org-refresh-properties org-effort-property 'org-effort)
+	    (org-refresh-properties "APPT_WARNTIME" 'org-appt-warntime)
 	    (setq org-todo-keywords-for-agenda
 		  (append org-todo-keywords-for-agenda org-todo-keywords-1))
 	    (setq org-done-keywords-for-agenda