[PATCHv3,Hurd] Add hardware watch support

[Joel Brobecker]

> > Many thanks for persisting with this patch.
> 
> I have to say I'm almost about to give up with submitting it.

I would be very interested in hearing your honest feedback on this.
I know it took a long time, and we're not always very responsive,
but we try our best. If we could hear what made you feel this way,
I would like to try to see if there are any ways we can improve
the situation for you.

-- 
Joel