ocamlPackages.ocaml_cryptgps: disable for OCaml ≥ 4.06

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

···
 {stdenv, fetchurl, ocaml, findlib}:
 
+if stdenv.lib.versionAtLeast ocaml.version "4.06"
+then throw "cryptgps is not available for OCaml ${ocaml.version}"
+else
+
 stdenv.mkDerivation rec {
   name = "ocaml-cryptgps-${version}";
   version = "0.2.1";