bug#37517: New rx.el breaks a number of packages - missing symbol rx-submatch-n

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Sun, 29 Sep 2019 14:57:23 +0200
> Cc: 37517@debbugs.gnu.org, cpitclaudel@gmail.com, theophilusx@gmail.com,
>         fmdkdd@gmail.com
> 
> > We've heard about one such symbol, which you consider internal, but
> > someone else didn't.  Why not provide that one symbol right now?  If
> > no other symbol is reported, that will be the only one, but I don't
> > see why it should wait for others to be granted that status.
> 
> Given that flycheck was rapidly fixed and the single internal function used 
> was tied to their particular rx use (because the old mechanism for extending 
> rx was under-documented, as alluded by Clément), do you still think we need 
> to add rx-submatch-n for the benefit of old flycheck versions?

Yes.  It's just one defalias...