(cua--extract-rectangle): Don't use \s in strings.

lisp/emulation/cua-rect.el

@@ -641,11 +641,11 @@ If command is repeated at same position, delete the rectangle."
 	     (if (= (point) (line-end-position))
 		 (setq bs (- r l)
 		       copy nil)
-	       (skip-chars-forward "\s\t" e)
+	       (skip-chars-forward " \t" e)
 	       (setq bs (- (min r (current-column)) l)
 		     s (point))
 	       (move-to-column r)
-	       (skip-chars-backward "\s\t" s)
+	       (skip-chars-backward " \t" s)
 	       (setq as (- r (max (current-column) l))
 		     e (point)))
        	     (setq row (if (and copy (> e s))