win32 文件读写 异步 I/O 操作

参考资料：

例子:异步读: Opening a File for Reading or Writing
https://msdn.microsoft.com/en-us/library/windows/desktop/bb540534(v=vs.85).aspx

第六章 Overlapped I/O，在你身后变戏法(1)
https://blog.csdn.net/yylooker2008/article/details/5668756