r1475: More kerberos work

r1475: More kerberos work

- We can now connect to hosts that follow the SPNEGO RFC, and *do not*
give us their principal name in the mechListMIC.
 - The client code now remembers the hostname it connects to

- We now kinit for a user, if there is not valid ticket already

- Re-introduce clock skew compensation

TODO:
 - See if the username in the ccache matches the username specified
 - Use a private ccache, rather then the global one, for a 'new' kinit
 - Determine 'default' usernames.
  - The default for Krb5 is the one in the ccache, then $USER
  - For NTLMSSP, it's just $USER

Andrew Bartlett