bug#29916: 26.0.90; CRLF in diff-command output breaks smerge hunk header parsing

[Eli Zaretskii]

> From: Richard Copley <rcopley@gmail.com>
> Date: Mon, 1 Jan 2018 11:51:51 +0000
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>, 29916@debbugs.gnu.org
> 
> By the way, I can also trigger the error at the top level (i.e., not inside
> a timer callback) by doing "diff-refine-hunk" interactively instead of
> "diff-goto-source".

That does show the error here.

So let's wait for Stefan to chime in, and then use your solution if no
objections are voiced.

Thanks.