windows下方便的相对路径和绝对路径的转换函数

相对路径到绝对路径
PathCombine
http://msdn2.microsoft.com/en-us/library/ms628544.aspx
绝对路径到相对路径
PathRelativePathTo
http://msdn2.microsoft.com/en-us/library/ms628614.aspx