I'm going to implement the krb5_kt_have_content() from Heimdal. Since
it adds a new API, I did a quick project page writeup:
http://k5wiki.kerberos.org/wiki/Projects/keytab_have_content_API
I don't think any feedback is required. The only edge case is that
non-iterable keytabs (i.e. the KDB keytab) will always be deemed to
have content.