Add mode to forward stdin and stdout to RunIO scripts

[Lysxia]

Close #76

(* cat.v *)
From SimpleIO Require Import SimpleIO.
Import IO.Notations.
RunIO IOMode Forward.
Definition cat : IO unit :=
  _ <- catch_eof
    (IO.fix_io (fun f _ =>
      input <- read_line ;;
      print_endline input ;;
      f tt :> IO unit) tt) ;;
  IO.ret tt.
RunIO cat.

echo "foo" | coqc cat.v

cc @zacque0

[liyishuai]

• QuickChick dev remove Dune upper bound coq/opam#3249