Sync a final change from pmail.el:

Chong Yidong  <cyd at stupidchicken.com>

(rmail-buffer-swapped): Mark as permanent local.

lisp/ChangeLog

+2009-01-23  Chong Yidong  <cyd@stupidchicken.com>
+
+	* mail/rmail.el (rmail-buffer-swapped): Mark as permanent local.
+
 2009-01-23  Glenn Morris  <rgm@gnu.org>
 	* Makefile.in (ELCFILES): Update.

lisp/mail/rmail.el

@@ -581,7 +581,7 @@ by substituting the new message number into the existing list.")
 
 (defvar rmail-buffer-swapped nil
   "If non-nil, `rmail-buffer' is swapped with `rmail-view-buffer'.")
-(make-variable-buffer-local 'rmail-buffer-swapped)
+(put 'rmail-buffer-swapped 'permanent-local t)
 
 (defvar rmail-view-buffer nil
   "Buffer which holds RMAIL message for MIME displaying.")