Fix broken dlltool --kill-at

[Nick Clifton]

Hi Danny,

> I forget this.   OK?
> 
> 2004-09-04  Danny Smith  <dannysmith@users.sourceforge,net>
> 
>         * doc/binutils.texi (dlltool):
> Update --add-underscore, --kill-at
>         documentation.

Approved - please apply.

Cheers
   Nick