bug#25987: 25.2; support gcc fixit notes

[Eli Zaretskii]

> Cc: tom@tromey.com, 25987@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 9 Mar 2017 19:49:19 +0200
> 
> On 09.03.2017 18:53, Eli Zaretskii wrote:
> 
> > So you suggest a separate minor mode, is that right?
> 
> A minor mode would be a good way toward the "quick-and-dirty" solution.
> 
> But we'd still want in-buffer indicators and a way to promptly 
> invalidate them as soon as the user makes some changes.
> 
> Ideally, also a way to refresh them automatically (e.g. as soon as the 
> user saves the changes). These requirements spell "Flymake" to me.

We could do both, of course.  Or Flymake could turn on that minor
mode.