bug#17309: 24.4.50; Typos in autotype info

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Cc: 17309@debbugs.gnu.org, Eli Zaretskii <eliz@gnu.org>
> Date: Tue, 22 Apr 2014 10:40:43 -0400
> 
> Indeed, I think "iff" is perfectly fine in docstrings, but we should
> refrain from using it in the Texinfo documentation.

Besides Glossary, autotype.info and message.info are the only manuals
that do, for the grand total of 3 (three) occurrences.  So I'd say we
follow our own advice quite well.