bug#25987: 25.2; support gcc fixit notes

[Eli Zaretskii]

> Cc: 25987@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 9 Mar 2017 18:37:30 +0200
> 
> If we look at Eclipse and friends, we can observe that (almost?) every 
> warning or error that the IDE shows to the user comes with a set of 
> actions, suggesting possible fixes, improvements, etc.
> 
> Thinking along these lines, the closest things we have are Flymake and 
> Flyspell. The third-party Flycheck is even better is several respects 
> (e.g. it can show a listing of all problems in the file buffer), but 
> sadly we won't be able to use it, since the primary author is sternly 
> against copyright assignment.

It sounds gross to ask people to use Flymake just to be able to use
something like this.