Merge pull request #20 from avsm/master

Add Conduit_xenstore
Merge pull request #21 from avsm/master

Better debugging via CONDUIT_DEBUG, and expose more type representations in Unix
Merge pull request #22 from avsm/master

Conduit 0.6.1
If depopt dns is used, it must be at least 0.10.0

findlib name dns.mirage minted for 0.10.0
Merge pull request #26 from mirage/dns-version

If depopt dns is used, it must be at least 0.10.0