bug#28349: 26.0.50; compilation mode syntax highlighting incorrect

[Eli Zaretskii]

> Date: Tue, 05 Sep 2017 18:26:57 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 28349@debbugs.gnu.org
> 
> > Error during redisplay: (jit-lock-function 2553) signaled
> > (void-function compilation-face)
> 
> This is because Tom's changes in 846870e removed the function
> compilation-face, which is still referenced in several places in
> compile.el.
> 
> Tom, could you take a look, please?

No comments, so I fixed this bug by resurrecting the lost function,
and I'm marking the bug done.

Thanks.