Handle differences in sig_class for OCaml 5.1.

Signed-off-by: Paul-Elliot <[email protected]>

Author: tmcgilchrist

src/loader/cmi.ml

@@ -1041,16 +1041,25 @@ and read_signature_noenv env parent (items : Odoc_model.Compat.signature) =
             else shadowed
           in
             loop (ModuleType mtd :: acc, shadowed) rest
+#if OCAML_VERSION < (5,1,0)
     | Sig_class(id, cl, rec_status, _) :: Sig_class_type _
       :: Sig_type _ :: Sig_type _ :: rest ->
+#else
+    | Sig_class(id, cl, rec_status, _) :: Sig_class_type _
+      :: Sig_type _ :: rest ->
+#endif
           let cl = read_class_declaration env parent id cl in
           let shadowed =
             if Env.is_shadowed env id
             then { shadowed with s_classes = Ident.name id :: shadowed.s_classes }
             else shadowed
           in
             loop (Class (read_type_rec_status rec_status, cl)::acc, shadowed) rest
+#if OCAML_VERSION < (5,1,0)
     | Sig_class_type(id, cltyp, rec_status, _)::Sig_type _::Sig_type _::rest ->
+#else
+    | Sig_class_type(id, cltyp, rec_status, _)::Sig_type _::rest ->
+#endif
         let cltyp = read_class_type_declaration env parent id cltyp in
         let shadowed =
           if Env.is_shadowed env id