func (v *List) Foreach(fn func(item interface{})) {
	for l := v; l != nil; l = l.Next() {
		fn(l.Data())
	}
}
func (v *List) Foreach(fn func(item interface{})) {
	for l := v; l != nil; l = l.Next() {
		fn(l.Data())
	}
}
// Foreach acts the same as g_list_foreach().
// No user_data argument is implemented because of Go clojure capabilities.