Fix dependencies: this library does not depend on mirage-{xen,unix}

It only depends on mirage-types (plus a set of standard libraries)

Signed-off-by: David Scott <dave.scott@citrix.com>
update CHANGES

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #9 from djs55/fix-deps

Fix dependencies: this library does not depend on mirage-{xen,unix}