Verify that our exported signature is compatible with V1_LWT.FLOW

The lib_test/test.ml checks this by instantiating the functor and constraining
to FLOW.

Signed-off-by: David Scott <dave.scott@citrix.com>
Regenerate OASIS

Signed-off-by: David Scott <dave.scott@citrix.com>
Add the missing types so the result of Vchan.Make can be constrained to FLOW

Fixes #11

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #23 from djs55/flow

Ensure we can constrain the output of Vchan.Make to V1_LWT.FLOW