- general cleanup [e-funcs, lint fixes, exit values, more error checking]
- add the ability to change the primary group group as login:group, or :group
*disabled*, until it is discussed.
- remove krb4 code since there is no more krb4 code in the tree.
- also make the old su behave like the pam su: su to the same user, does
not ask for a password.
- split out shared code into a separate file.
