bug#6304: 23.2; advising yank

[Leo]

I have been seeing this for a while but just find this reproducible
case:

1. (defadvice yank (after random-advice activate)
      (message "hello world"))

2. C-h f yank RET

The string "This function is advised." is not highlighted with the
warning face.

In GNU Emacs 23.2.5 (x86_64-apple-darwin10.3.0)
 of 2010-05-28

Leo