bug#49730: 28.0.50; There should be a way to mark a generalised variable as obsolete

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> We don't have a way to make a generalised variable obsolete, I think?  I
> think it would be helpful if we had.
>
> I haven't looked at how to implement it, but marking the symbol in some
> way, and then having the byte compiler examine it (when expanding setf
> forms) and outputting a warning doesn't immediately seem impossible.

It was very simple.  Now added to Emacs 29.