bug#27622: Trying to improve the speed of linum-mode

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: ybbs.daans@hotmail.com,  27622@debbugs.gnu.org
> Date: Sun, 30 Jul 2017 22:06:31 -0400
> 
> Eli Zaretskii wrote:
> 
> >> Time to obsolete linum.el (which now has two replacements)?
> >
> > Probably.  But do we move it to obsolete right away, or just mark its
> > main entry "obsolete"?
> 
> I would move it to obsolete, but add a manual autoload so that M-x
> linum-mode still works. Cf iswitchb-mode in icomplete.el.

Fine with me, thanks.