Add ocaml-{ctypes,opasswd}, dependencies of modern xapi

Signed-off-by: David Scott <dave.scott@citrix.com>
Update to ocaml-opasswd.0.9.3

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #398 from djs55/ctypes

Add ocaml-{ctypes,opasswd}, dependencies of modern xapi