Fixed Module#to_s and #name for #const_set modules

src/class.c

@@ -2178,6 +2178,9 @@ mrb_mod_const_set(mrb_state *mrb, mrb_value mod)
 
   mrb_get_args(mrb, "no", &id, &value);
   check_const_name_sym(mrb, id);
+  if (mrb_type(value) == MRB_TT_CLASS || mrb_type(value) == MRB_TT_MODULE) {
+    setup_class(mrb, mrb_class_ptr(mod), mrb_class_ptr(value), id);
+  }
   mrb_const_set(mrb, mod, id, value);
   return value;
 }