说明：  libxml是一个开源的库，linux下解析xml文件经常用到，进行一些创读增删的操作。 在这里，本测试程序源代码，来处理这个xml换行问题。
(Libxml is an open source library, under Linux is often used to parse the XML file, for some gen read add or delete operation. Here, the test program source code, to deal with the XML line problem.)