bug#20728: 25.0.50; grep and grep-find templates should have a place holder for the --color argument

[Eli Zaretskii]

> Cc: 20728@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 4 Jun 2015 18:18:55 +0300
> 
> how would you implement automatic support for that variable in it,
> if not using a template?

  (cond
    ((eq grep-highlight-matches 'never)
      "--color=never")
    ((eq grep-highlight-matches 'auto)
      "--color=auto"

etc., you get the idea.