添加设计模式及例子，包括：单例、抽象工厂、适配器、桥接、观察者模式

DesignPattern/ObserverPattern/ObserverMain.h

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+//
+// Created by xiemenghui on 2018/7/21.
+//
+
+#ifndef DESIGNPATTERN_OBSERVERMAIN_H
+#define DESIGNPATTERN_OBSERVERMAIN_H
+
+#include "concrete_subject.h"
+#include "concrete_observer.h"
+
+#ifndef SAFE_DELETE
+#define SAFE_DELETE(p) { if(p){delete(p); (p)=nullptr;} }
+#endif
+
+void ObserverMain();
+
+#endif //DESIGNPATTERN_OBSERVERMAIN_H