bug#24786: 25.1; Misleading documentation/news for text-quoting-style

[Vasilij Schneidermann]

> Did you look at the state of affairs on the emacs-25 branch?  If not,
> please do: I think at least some of these problems were fixed there.
> If they are still not fixed, or you cannot figure out how to fix them,
> please tell the details: where did you read or saw behavior that
> disallows turning off the conversion of quotes.

Thanks for the hint, I'm on Emacs 25.1 where the behavior is as
described.  As you've pointed out, 25.2 does not take
`text-quoting-style' into account for both `message' and
`format-message', additionally to that the (incompatible) change has
been documented and the docstring updated to clarify that `grave` is the
setting to disable post-processing.