Compatibility: XEmacs does not have user-emacs-directory, use user-init-directory instead

* lisp/org-compat.el (user-emacs-directory): If not bound, define as an alias to
  `user-init-directory´ so that XEmacs continues to be happy with Org.

lisp/org-compat.el

@@ -113,6 +113,11 @@ any other entries, and any resulting duplicates will be removed entirely."
 
 ;;;; Emacs/XEmacs compatibility
 
+(eval-and-compile
+  (when (and (not (boundp 'user-emacs-directory))
+	     (boundp 'user-init-directory))
+    (defvaralias 'user-emacs-directory 'user-init-directory)))
+
 ;; Keys
 (defconst org-xemacs-key-equivalents
   '(([mouse-1] . [button1])