bug#56641: Deprecate `lsh`

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: stefankangas@gmail.com,  mattiase@acm.org,  56641@debbugs.gnu.org
> Date: Wed, 20 Jul 2022 11:20:14 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > If it's rare enough (as it should be), I don't see the annoyance.  Am
> > I missing something?
> 
> It might be rare, but there's nothing wrong with using lsh for its
> intended purpose, which is handling negative numbers correctly in
> several different situations.

The point is that people could use lsh because they don't realize they
could use ash instead.  If one really must use lsh, there's always
with-no-warnings, which is IMO fine for the rare situations where it's
needed.

> Byte-compiler warnings are supposed to point out problems.

And this could indeed be a problem: that the programmer is not aware
of a better alternative.

So I don't see a problem with warning in this case, I just don't want
us to pretend this function is "obsolete", because it isn't.