bug#37659: rx additions: anychar, unmatchable, unordered-or

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Thu, 13 Feb 2020 20:16:28 +0100
> Cc: Eli Zaretskii <eliz@gnu.org>, Phil Sainty <psainty@orcon.net.nz>,
>         37659@debbugs.gnu.org
> 
> > Simplest would be to remove it in Emacs 27, and merge that change into 
> > master.
> 
> Right, introducing it already deprecated doesn't make sense at all. I'll do 
> it in emacs-27 if Eli doesn't mind too much (patch attached).

Fine with me, thanks.