Update to shared-memory-ring.1.1.0
Update to shared-memory-ring.1.1.0

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@citrix.com>

mirage/ocaml-xenstore-server,djs55/ocaml-xenstore-server,mirage/ocaml-xenstore-server