Copy `iv` table with `#prepend`; fix
In addition, stop eager allocation of `mt` table.
MODIFY
src/class.c
src/class.c
@@ -1497,7 +1497,8 @@ mrb_prepend_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
origin->super = c->super;
c->super = origin;
origin->mt = c->mt;
- c->mt = mt_new(mrb);
+ c->mt = NULL;
+ origin->iv = c->iv;
mrb_field_write_barrier(mrb, (struct RBasic*)c, (struct RBasic*)origin);
c->flags |= MRB_FL_CLASS_IS_PREPENDED;
}

Copy `iv` table with `#prepend`; fix #5309

In addition, stop eager allocation of `mt` table.