说明：  utf8编码，解码程序，实现了utf8,unicode,ansi之间的转换函数，还提供了一个utf8字符串迭代器，使用这个迭代器可以方便的遍历utf8所表示的每一个真实字符
(utf8 encoding, decoding procedures, the utf8, unicode. ansi between the transfer function, it also provided a utf8 string iteration devices, the use of the iterative device can easily traverse the utf8 expressed by every one of the true characters)