Ticket 6400: krb5_merge_authdata

[Sam Hartman]

I'd like to draw your attention to ticket 6400 which introduces a new
public API: krb5_merge_authdata.

There are a number of cases we've seen in the KDC where you want to
combine two authdata sequences.  This also comes up in the library
because you'd like to get the authdata both from the ticket and
authenticator.

I've introduced this API because I needed something like it to resolve
a GSS-API bug.  I have not removed the similar private API from the
guts of the KDC introduced by Luke's changes.

--Sam