bug#56641: Deprecate `lsh`

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Tue, 19 Jul 2022 12:20:01 -0400
> Cc: Eli Zaretskii <eliz@gnu.org>, 56641@debbugs.gnu.org
> 
> Mattias Engdegård <mattiase@acm.org> writes:
> 
> > Adding a few words to the doc string may suffice, but a byte-compiler
> > warning would help.
> 
> What we have done in such cases is declare it obsolete but add a comment
> that we want to keep it around for longer.  See `interactive-p', that
> was not deleted in Emacs 28 despite having been obsolete for over a
> decade.

This is not what "obsolete" means and is about, so let's not abuse it
for this purpose.

I'm okay with introducing some new special attribute for such cases,
i.e. when the use of a function or a variable is discouraged for
whatever reasons, so that the byte-compiler could warn about that.
Just let's not called them "obsolete", because they aren't.