ocamlPackages.mlgmp: disable for OCaml ≥ 4.03

pkgs/development/ocaml-modules/mlgmp/default.nix

···
 {stdenv, fetchurl, ocaml, findlib, gmp, mpfr, ncurses }:
 
+if stdenv.lib.versionAtLeast ocaml.version "4.03"
+then throw "mlgmp is not available for OCaml ${ocaml.version}" else
+
 let
   pname = "mlgmp";
 in