Remove more XEmacs compat functions from gnus-util.el

* lisp/gnus/gnus-util.el (gnus-put-display-table): Remove.
(gnus-get-display-table): Remove.
(gnus-format-message): Remove.

lisp/gnus/gnus-int.el

@@ -164,7 +164,7 @@ If CONFIRM is non-nil, the user will be asked for an NNTP server."
        (gnus-open-server gnus-select-method)
        gnus-batch-mode
        (gnus-y-or-n-p
-	(gnus-format-message
+	(format-message
 	 "%s (%s) open error: `%s'.  Continue? "
 	 (car gnus-select-method) (cadr gnus-select-method)
 	 (gnus-status-message gnus-select-method)))