🚀 go-pugleaf

If the rmail command is run from a window not containing RMAIL, but
there is window displaying RMAIL, then currently a second window on
RMAIL is created, instead of just popping to original RMAIL window.
(Got that?)  Anyway, this fixes that behavior:  it won't create
redundant rmail windows.

*** /usr/local/lib/gnuemacs/lisp/rmail.el	Thu Feb 18 17:49:46 1988
--- /usr/local/lib/gnuemacs/lisp/new-rmail.el	Fri Sep 23 09:39:54 1988
***************
*** 104,109 ****
--- 104,111 ----
  	    rmail-last-rmail-file rmail-last-file))
    (let* ((file-name (expand-file-name (or file-name-arg rmail-file-name)))
  	 (existed (get-file-buffer file-name)))
+      (if (and existed (get-buffer-window existed))
+ 	(pop-to-buffer existed))
      ;; Like find-file, but in the case where a buffer existed
      ;; and the file was reverted, recompute the message-data.
      (if (and existed (not (verify-visited-file-modtime existed)))