单键模式模板类的实现，在使用的时候直接DECLARE_SINGLETON_CLASS( class_name )就可以将你的类设置为单键模式的，同时使用双重锁定保证多线程安全；-Single mode realization of template classes in the use of a time when direct DECLARE_SINGLETON_CLASS (class_name) can be set to your type of one-button model, while the use of multi-threaded double-lock guarantee security