Restrict zmq-async minimal OCaml/JST version (#14930)
Restrict zmq-async minimal OCaml/JST version (#14930)

* Restrict zmq-async minimal version

Due to an issue with where glibc puts `makedev` and where Core < v0.11
(a dependency of Async) expects `makedev` this package will always fail
to build. It is fixed in Core v0.11 but that requires at least OCaml
4.04.1 so we're restricting the minimal version.

A similar change is planned upstream, the next release of ZMQ will
probably drop 4.03 support altogether (also in the base library and Lwt
bindings): https://github.com/issuu/ocaml-zmq/pull/93

This PR is a more conservative approach to limit the disruption to users
of the release on OPAM.

* last ounit release is not compatible

fdopen/opam-repository-mingw,fdopen/opam-repository-mingw