[idn] Preserve case for IDNs during transportation

["Edmon Chung" <edmon@neteka.com>]

Perhaps we should preserve case for IDNs during transportation, as we do
today with English only names.  Nameprep can be done at the server as well
as the client, but is optional for the client during request and mandatory
for the client if DNSSEC is required.

That is:

1. Application ToACE multilingual domain name
2. Send ACE domain to server without doing Nameprep
3. If fail go to 5.  If successful go to 4.
4. Authenticate and match response by first Namepreping both and comparing.

5. Send again with Namepreping, if successful go to 4, if fail then NX
domain

This way, case can be preserved during transportation just as it is today.
Also, some browsers do the same with English domain names right now anyway:
first send case preserved name, if fails, lowercase (or uppercase) and send
again.

Edmon