Mark display-buffer-function as obsolete.

* lisp/window.el (display-buffer-function): Mark as obsolete.

Fixes: debbugs:12166

etc/NEWS

@@ -735,6 +735,7 @@ in Emacs 24.1:
 **** `special-display-frame-alist'
 **** `special-display-buffer-names'
 **** `special-display-function'
+**** `display-buffer-function'
 
 ** Completion
 

lisp/ChangeLog

@@ -1,6 +1,7 @@
 2012-09-16  Chong Yidong  <cyd@gnu.org>
 
 	* window.el (special-display-popup-frame): Doc fix (Bug#8853).
+	(display-buffer-function): Mark as obsolete.
 
 	* progmodes/compile.el (compilation-parse-errors): Accept list
 	values similar to font-lock-keywords (Bug#12136).  Suggested by

lisp/window.el

@@ -4551,6 +4551,9 @@ of the window used."
 	  (function :tag "function"))
   :group 'windows)
 
+(make-obsolete-variable 'display-buffer-function
+			'display-buffer-alist "24.3")
+
 ;; Eventually, we want to turn this into a defvar; instead of
 ;; customizing this, the user should use a `pop-up-frame-parameters'
 ;; alist entry in `display-buffer-base-action'.