Use "Encoding" parameter for asx file

http://msdn.microsoft.com/library/windows/desktop/dd563989%28v=vs.85%29.aspx

This is needed for my environment.
When this tag does not exist, WMP interprets a file by a default character code(MS932 for me).

It may be necessary to convert tag information(I don't know).  My tags are written by utf-8.