need another combinator for read that explicitly fails on EOF
need another combinator for read that explicitly fails on EOF

djs55/ocaml-vchan,djs55/ocaml-vchan,samoht/ocaml-vchan,djs55/ocaml-vchan,mirage/ocaml-vchan,mirage/ocaml-vchan,samoht/ocaml-vchan,samoht/ocaml-vchan,mirage/ocaml-vchan