Honour existing restrictions when regenerating the agenda

* lisp/org.el: Honour existing restrictions when regenerating the agenda

Narrowed org buffers are now retained when regenerating the agenda
with org-agenda-redo

lisp/org.el

@@ -16498,13 +16498,13 @@ When a buffer is unmodified, it is just killed.  When modified, it is saved
 	(rea (concat ":" org-archive-tag ":"))
 	     bmp file re)
     (save-excursion
-      (save-restriction
-	(while (setq file (pop files))
-	  (catch 'nextfile
-	    (if (bufferp file)
-		(set-buffer file)
-	      (org-check-agenda-file file)
-	      (set-buffer (org-get-agenda-file-buffer file)))
+      (while (setq file (pop files))
+	(catch 'nextfile
+	  (if (bufferp file)
+	      (set-buffer file)
+	    (org-check-agenda-file file)
+	    (set-buffer (org-get-agenda-file-buffer file)))
+	  (save-restriction
 	    (widen)
 	    (setq bmp (buffer-modified-p))
 	    (org-refresh-category-properties)