Interop/Compat: 3DES used in AS-REP despite no client support

[Jeffrey Altman]

When creating or modifying the cross realm principals with
MIT kadmin, you must specify the list of enc:salt combinations
you wish created for that principal.

If you do not specify a list, the default list from kdc.conf
will be used.

You use the "-e enc:salt ..." option as documented here:

http://web.mit.edu/kerberos/krb5-1.4/krb5-1.4.3/doc/krb5-admin/Adding-or-Modifying-Principals.html#Adding%20or%20Modifying%20Principals

For the cross-realm principals, if your Windows servers are pre 2003 
SP1, they must be restricted to DES-CBC-MD5 and DES-CBC-CRC.   If the
servers are 2003 SP1 and later you can also include RC4-HMAC.

You do not need to modify the enctypes for all client and service
principals, just those used for the cross realm relationships with
Windows domains.