ocamlPackages: make explicit some version requirements

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

···
 { stdenv, fetchurl, ocaml, jbuilder, findlib }:
 
+if !stdenv.lib.versionAtLeast ocaml.version "4.03"
+then throw "base is not available for OCaml ${ocaml.version}" else
+
 stdenv.mkDerivation {
   name = "ocaml${ocaml.version}-base-0.9.0";
 

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

···
 , bos, cmdliner, ocamlgraph
 }:
 
+if !stdenv.lib.versionAtLeast ocaml.version "4.03"
+then throw "functoria is not available for OCaml ${ocaml.version}" else
+
 stdenv.mkDerivation rec {
 	name = "ocaml${ocaml.version}-functoria-${version}";
 	version = "2.0.2";

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

···
 { stdenv, fetchFromGitHub, ocaml, findlib, owee }:
 
+if !stdenv.lib.versionAtLeast ocaml.version "4.04"
+then throw "spacetime_lib is not available for OCaml ${ocaml.version}" else
+
 stdenv.mkDerivation rec {
   name = "ocaml${ocaml.version}-spacetime_lib-${version}";
   version = "0.1.0";