updated classic ASP base64 encoder, AD script for better unicode support

In many cases, Base64 encoding function in the IIS/AD bundle didn't work for names with multibyte characters. I replaced the contents of the base64.asp utility with the function [here](https://code.google.com/p/asplite/source/browse/trunk/Base64.asp?spec=svn31&r=31) and added a UTF-8 encoding function in the AD script itself. A number of Zendesk customers have used the new scripts successfully with multibyte names.

**NB**: I have not contacted the author of the new Base64 encoding function, but I can certainly do so before merging; I'm not sure what the protocol is here.