bug#39274: Warn when using obsolete command interactively

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Cc: 39274@debbugs.gnu.org
> Date: Sat, 25 Jan 2020 20:22:52 +0100
> 
> >>> (message "The `%s' command is obsolete since version %s, use `%s' instead"
> >>>          obsolete-name version current-name)
> >>
> >> Where and when will this warning be displayed?
> >
> > I was thinking of something along the lines of the below patch.

So for obsolete commands we will now display 2 messages, one after the
other?