测试回调机制CALLBACK。DLL文件调用为动态调用。此示例在VS2008下测试通过。注意在DLL中需要在DEF文件里的EXPOERTS下面添加tester，编译后将callbackdll.dll添加到dllimporttest的DEBUG目录下。 -Test callback mechanism CALLBACK. DLL file is called as dynamic invocation. This example in