bindings: Add Sanlk_disk.to_/from_internal helper functions
bindings: Add Sanlk_disk.to_/from_internal helper functions

Signed-off-by: Si Beaumont <a0992b7f1f450b4c7716d34b81a2d6f0877ae11a@citrix.com>

simonjbeaumont/ocaml-sanlock