rmail breaks if find-file-visit-truename is t

[Albumen Petrofsky]

In 21.1 and in current cvs head,

In .emacs I set find-file-visit-truename to t and rmail-file-name to
something that contains symbolic links.  If I M-x rmail when an rmail
buffer already exists, rmail doesn't realize that the buffer is
already there, and this leads to the message counters getting screwed
up.

This fix appears to work:

--- rmail.el.~1.352.~   Fri Jan 11 13:23:40 2002
+++ rmail.el    Thu Jan 31 00:18:58 2002
@@ -625,7 +625,7 @@
                   (list (read-file-name "Run rmail on RMAIL file: "))))
   (rmail-require-mime-maybe)
   (let* ((file-name (expand-file-name (or file-name-arg rmail-file-name)))
-        (existed (get-file-buffer file-name))
+        (existed (find-buffer-visiting file-name))
         ;; This binding is necessary because we must decide if we
         ;; need code conversion while the buffer is unibyte
         ;; (i.e. enable-multibyte-characters is nil).