bug#28349: 26.0.50; compilation mode syntax highlighting incorrect

[Eli Zaretskii]

> From: Richard Copley <rcopley@gmail.com>
> Date: Sat, 16 Sep 2017 19:30:36 +0100
> Cc: 28349@debbugs.gnu.org
> 
> I had my own file-name-handler-alist entry that clobbered the match
> data by calling (unmsys--filename) from "subr.el". Not an Emacs bug.
> 
> Ignore my previous attribution of this to file-truename.

OK, thanks for looking into this.