[krbdev.mit.edu #155] security concern with using home directory for .k5login

[Greg Hudson via RT]

#6792 implements k5login_directory, which fulfills the purpose of 
k5login_location from the patch.  #7583 implements the localauth 
pluggable interface, which provides enough rope to disable an2ln as a 
k5userok facility, thus fulfilling the purpose of k5login_required from 
the patch.