bug#17787: 24.4.50; Making `linum-mode` more efficient -- no need to run multiple times.

[Eli Zaretskii]

> Date: Sun, 15 Jun 2014 12:11:52 -0700
> From: Keith David Bershatsky <esq@lawlist.com>
> 
> Linum-mode could be made more efficient [...]

Can I persuade you (and everyone else) to please forget linum-mode
ever existed, and never to remember that?  If someone wants line
numbers in Emacs, could they please use Stefan's nlinum-mode instead?

linum-mode is a terrible idea squared.  It abuses post-command-hook.
It moves overlays and changes the window's display margins on the fly,
and by that kills almost every redisplay optimization (so don't try
using it if you are accustomed to many windows and many frames,
especially large ones).  It is evil.  We certainly shouldn't make it
more efficient.  It should die a horrible death.  Soon.

Thank you.