xen_4_10: use OCaml 4.05

pkgs/applications/virtualization/xen/4.10.nix

···
 { stdenv, callPackage, fetchurl, fetchpatch, fetchgit
+, ocaml-ng
 , withInternalQemu ? true
 , withInternalTraditionalQemu ? true
 , withInternalSeabios ? true
···
       else throw "this xen has no qemu builtin";
   };
 
-})) args
+})) ({ ocamlPackages = ocaml-ng.ocamlPackages_4_05; } // args)