His comments are:

This patch fixes the problem of modern Kerberos using "derived keys"
to encrypt the authenticator by disabling the authenticator check
for all derived keys enctypes.

I think I've got all the bugfixes that Jeffrey and I discussed rolled
into this.  There were some problems with Jeffrey's code to convert
the authenticator's Kerberos timestring into struct tm (e.g. Z, -1900;
it helps to have an actual decryptable authenticator to play with).
So I've shamelessly pushed in my code, while stealing some bits from
Jeffrey.