hg.octave.org and gnulib subrepo update

[John W. Eaton]

After much thrashing about and getting some help from Jordi, I have 
moved the hg.octave.org repos to a Digital Ocean server (the one that is 
running the buildbot master) and off of Dreamhost.  Now the update 
script should be working again for our hg clone of gnulib.

Once that was done, I updated the gnulib subrepo on stable and default. 
This task doesn't seem to be on the release checklist, but it probably 
should be.

I also changed the subrepo address to use hg-new.octave.org.  We can 
switch it back once the DNS change for hg.octave.org makes its way 
around the web.

jwe