Freeze break for yelp-tools

[Shaun McCance <shaunm gnome org>]

Hi all,

I'm not sure where yelp-tools fits into our release sets and how it's
affected by the freezes. Certainly it's not something users use, but
it's part of our developer stack.

There's a bug report asking for `yelp-check hrefs` to return non-zero
when there are broken hrefs to report:

https://bugzilla.gnome.org/show_bug.cgi?id=726763

This is the patch I have to implement that:

http://fpaste.org/87654/55040601/

It's the same code I use to make `yelp-check links` return non-zero when
there are broken internal links to report:

https://git.gnome.org/browse/yelp-tools/tree/tools/yelp-check.in#n441

Can I put this in for 3.12.0?

Thanks,
Shaun