[krbdev.mit.edu #6708] logging preauth (patch available)

[Jeff Blaine via RT]

Is this patch wanted?

Example:

     Apr 24 13:10:04 kdc.our.org krb5kdc[30257](info): PREAUTH
     xxx.yy.10.113: VALID: authtime 1272127234, jblaine at MYREALM.OUR.ORG
     for krbtgt/MYREALM.OUR.ORG at MYREALM.OUR.ORG

kdc/kdc_util.h
     proto for new log_preauth()

kdc/kdc_util.c
     new function log_preauth(), copied and modified from
     existing log_as_req()

kdc/do_as_req.c
     call log_preauth if the errcode from check_padata() is 0