一个双字节转4字节的字符处理函数，用于不同系统/编程语言间字符对应长度不同时的转换，其中已考虑大小端问题。附网上摘录的字节序资料-A two-byte transfer 4-byte character handling function for the character corresponding to the length of the conversion is not the same in different systems/programming language, which h