Comment 11 for bug 640516

Test case:

(assert
 (handler-case
     (sb-ext:with-timeout 10
       (let (to)
         (handler-bind ((sb-ext:timeout (lambda (c)
                                          (unless to
                                            (setf to t)
                                            (sleep 2)
                                            (continue c)))))
           (sb-ext:with-timeout 0.1 (sleep 1) t))))
   (sb-ext:timeout ()
     nil)))