(kill-rectangle): In read-only buffer, do record

the rectangle for later yanking.

lisp/rect.el

@@ -138,6 +138,10 @@ Value is list of strings, one for each line of the rectangle."
 Calling from program, supply two args START and END, buffer positions.
 But in programs you might prefer to use `delete-extract-rectangle'."
   (interactive "r")
+  (if buffer-read-only
+      (progn
+	(setq killed-rectangle (extract-rectangle start end))
+	(barf-if-buffer-read-only)))
   (setq killed-rectangle (delete-extract-rectangle start end)))
 
 ;;;###autoload