dolist doc fix.

(dolist): Mention that there's a nil block

lisp/ChangeLog

 2011-08-02  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
+	* emacs-lisp/cl-macs.el (dolist): Mention that there's a nil block
+	(bug#4433).
+
 	* ido.el (ido-mode): Switch off the message if called
 	non-interactively.
 

lisp/emacs-lisp/cl-macs.el

@@ -1233,6 +1233,7 @@ Valid clauses are:
   "Loop over a list.
 Evaluate BODY with VAR bound to each `car' from LIST, in turn.
 Then evaluate RESULT to get return value, default nil.
+An implicit nil block is established around the loop.
 
 \(fn (VAR LIST [RESULT]) BODY...)"
   (let ((temp (make-symbol "--cl-dolist-temp--")))