bug#24353: 25.1.1: looking-back wrong info

[Drew Adams]

> >>> How does this change help Emacs users?
> >>
> >> It forces Emacs Lisp programmers to include the last argument,
> >
> > It certainly does not.  It does NOT force anything.
> > It only misleads.  It doesn't even explicitly recommend.
> 
> Well, at least the byte compiler sees the advertised calling convention,
> and warns when it's violated. So the encouragement is there.

That's true, and a good point.

It's misleading to show the signature wrong.  It's
especially unhelpful to do ONLY that.

Encouragement, recommendation, admonition, and even warning,
can help.  The more explicit, the better.  The more it helps
users _understand_ (e.g., say WHY), the better.