[krbdev.mit.edu #7647] let ktutil support non-default salts

[Sam Hartman via RT]

Especially because of the random salt discussion on kitten, if I were
going to implement this I'd like to see something like a

krb5_get_init_creds_probe_etype_info that probes the salt and encryption
types the KDC offers for a principal.  Such an interface should take
gic_opts mostly for FAST related stuff and ideally re-use most/all of
the GIC mechanisms.

--Sam