Add vhd-tool .spec from sanibel-lcm

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
When copying disk blocks, never encrypt

Normal disk block accesses are unencrypted, and this is described in
the XenServer 6.2 user security document. Make this explicit by setting
'encryption = never' in sparse_dd.conf

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Add Mike's ocaml-nbd changes

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #25 from djs55/vhd

Add vhd-tool .spec from sanibel-lcm