org-compat: obsolete org-activate-mark.

* lisp/org-compat.el (org-activate-mark): Make obsolete.

The activate-mark function was introduced in Emacs 23 and
org-activate-mark wasn’t called anywhere in the code base.

lisp/org-compat.el

@@ -287,17 +287,8 @@ Works on both Emacs and XEmacs."
 	     (> (point) (region-beginning)))
     (exchange-point-and-mark)))
 
-;; Emacs 22 misses `activate-mark'
-(if (fboundp 'activate-mark)
-    (defalias 'org-activate-mark 'activate-mark)
-  (defun org-activate-mark ()
-    (when (mark t)
-      (setq mark-active t)
-      (when (and (boundp 'transient-mark-mode)
-		 (not transient-mark-mode))
-	(setq transient-mark-mode 'lambda))
-      (when (boundp 'zmacs-regions)
-	(setq zmacs-regions t)))))
+;; Old alias for emacs 22 compatibility, now dropped
+(define-obsolete-function-alias 'org-activate-mark 'activate-mark)
 
 ;; Invisibility compatibility