canonicalize, as_req, pa_svr_referral, pa_server_referral

[Luke Howard]

> So, my question is to what extent do we need to support service name
> aliases in the AS?  If the answer is not much, let's remove that from
> the client and server and lose enc_padata.

Windows interop does require support for realm aliases in the AS-REQ  
case (because Windows clients will send the NetBIOS name in an AS-REQ  
unless you are logging on with a UPN).

enc_padata is just for TGS-REP. I'm happy to remove that code.

-- Luke