func (r *Router) Combo(pattern string, h ...Handler) *ComboRouter {
	return &ComboRouter{r, pattern, h, map[string]bool{}, nil}
}
func (r *Router) Combo(pattern string, h ...Handler) *ComboRouter {
	return &ComboRouter{r, pattern, h, map[string]bool{}, nil}
}
// Combo returns a combo router.