Improve Kerberos support in ssh2:
- Change the WITH_KERBEROS knob into a WITHOUT_KERBEROS knob so kerberized
ssh2 automatically is built when MIT Kerberos is installed, unless the
WITHOUT_KERBEROS knob is defined.
- Check for a library unique to MIT Kerberos to make sure it's not Heimdal
that KRB5_HOME accidentally points to.
- Add dependency on security/krb5 when built with Kerberos support.
- When compiled with Kerberos support also turn it on by default in client
and server config files and set "PermitRootLogin" to "nopwd" to only allow
those with root tickets declared in ~root/.k5login" to login as root. 
Ssh2 now should work out of the box in an environment using MIT Kerberos.
Submitted by: Peter Losher <Peter_Losher@isc.org>  (kerberos-patch-*)
Tested by: Peter Losher <Peter_Losher@isc.org>
Submitted by: maintainer
Strange commit log formatting to prevent
ambiguous "Submitted by" lines by: committer