bug#47368: 28.0.50; map-elt returns nil without "deprecated" TESTFN

[Michael Heerdegen]

"Basil L. Contovounesios" <contovob@tcd.ie> writes:

> Just some code archaeology for more context:
>
> - Pre-Emacs-25 map-elt used assoc.
> - Emacs 25 map-elt used alist-get without TESTFN.
> - Emacs 26 map-elt gained TESTFN at the same time that alist-get did,
>   in https://bugs.gnu.org/27584.
> - Emacs 27 deprecated map-elt's TESTFN.

And `map-put!' has been added recently.  For alists it compares with
`equal', and it's used by the setter for the general `map-elt' variable,
so we currently don't have consistence.

Michael.