bug#64391: buffer narrowing slowdown regression in emacs 29

[Gregory Heytings]

> > > I have one question about the new `with-restriction` macro: if it is 
> > > intended as a convenience macro for unlabelled narrowing as well, 
> > > shouldn't it then expand to the obvious
> > >
> > >  (save-restriction
> > >    (narrow-to-region BEG END)
> > >    BODY)
> > >
> > > instead the much more expensive call to a helper function?
> >
> > Yes.  In fact now that we have a separate function for the labeled 
> > case, we can remove the funcall in both cases.  Patch attached.
>
> You are killing me.

???  That wasn't meant for the release branch.