bug#59920: [PATCH] Make checkdoc warn if not using lexical-binding

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Fri, 9 Dec 2022 04:42:00 -0800
> Cc: 59920@debbugs.gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Thanks, but I think this should be optional behavior.  checkdoc is not
> > only used by us.
> 
> The idea here is to encourage others to upgrade to lexical-binding, as
> we are already done (at least in emacs.git, if not yet in GNU ELPA).
> 
> I'm actually more concerned that this check will not reach enough users.
> So while I think an option is a good idea, the best default is IMO to
> have it enabled.

I said nothing about defaults.  I just think we should allow turning
off this warning.