bug#62419: 28.2; Elisp let-bound buffer-local variable and kill-local-variable

[Stefan Monnier]

> Just for the record I’ve been running using essentially this patch (but
> with !=) since you suggested it and have not had any problems.

Thanks for confirming it fixes the problem for you.
I pushed it to `master` (doesn't seem "obviously safe" enough for `emacs-29`).

> FWIW I also think the change to avoid `let` binding
> `auto-fill-function` in `normal-mode` is good.

I also pushed it to `master`.


        Stefan