bug#40693: 28.0.50; json-encode-alist changes alist

[Eli Zaretskii]

> Cc: contovob@tcd.ie, darthandrus@gmail.com, 40693@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Wed, 29 Apr 2020 18:02:52 +0300
> 
> > Sounds like a somewhat hairy issue.  Then let's put this on master
> > first.  If this turns out to be a very popular change, and no one
> > complains, we could later back-port it to some 27.x version.
> 
> *shrug*, I'm certainly not going to insist, but we could push the 
> "slightly slower" simple patch to emacs-27, and go with Basil's refactor 
> (sounds exciting!) on master.

I'd rather not risk an extra pretest just because of an issue that has
been with us for a long time.  Emacs 27 is already way too late.