bug#42296: 27.0.91; Correct manual entry for 'concat' w.r.t. allocation [PATCH]

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Thu, 9 Jul 2020 19:56:59 +0200
> Cc: 42296@debbugs.gnu.org
> 
> > This loses too much useful information, IMO.  Let's please say that
> > the result is sometimes ("frequently"?), but not always, a new string,
> > and that programs should not rely on that aspect.
> 
> Here is a new version that adds this information, and recommends 
> copy-sequence for mutability.

That's not really what I asked for.

And how does mutability enter the picture?  We could say something
about it (but then we'd have to be less terse), but that doesn't in
any way replace the need to say that in many cases the value will be a
new string, IMO.

Thanks.