included_modules, origin fix

Prepended modules would include their origin ICLASS

src/class.c

@@ -1000,10 +1000,11 @@ mrb_mod_included_modules(mrb_state *mrb, mrb_value self)
 {
   mrb_value result;
   struct RClass *c = mrb_class_ptr(self);
+  struct RClass *origin = c->origin;
 
   result = mrb_ary_new(mrb);
   while (c) {
-    if (c->tt == MRB_TT_ICLASS) {
+    if (c != origin && c->tt == MRB_TT_ICLASS) {
       if (c->c->tt == MRB_TT_MODULE) {
         mrb_ary_push(mrb, result, mrb_obj_value(c->c));
       }