When trying to compile recent OpenSSH-portable snapshots on OpenBSD 3.1, I get:

readpass.c: In function `read_passphrase':
readpass.c:100: `RPP_ECHO_ON' undeclared (first use in this function)
readpass.c:100: (Each undeclared identifier is reported only once
readpass.c:100: for each function it appears in.)
readpass.c:100: `RPP_ECHO_OFF' undeclared (first use in this function)
readpass.c:105: `RPP_REQUIRE_TTY' undeclared (first use in this function)
readpass.c:121: warning: implicit declaration of function `readpassphrase'
*** Error code 1

The required defines are in openbsd-compat/readpassphrase.h, and they assume
that HAVE_READPASSPHRASE is undefined.  If I undefine HAVE_READPASSPHRASE,
make clean, and make, everything compiles, but when I try to turn on sshd,
I get:

/usr/local/etc/sshd_config: line 68: Bad configuration option: KerberosAuthentication
/usr/local/etc/sshd_config: line 69: Bad configuration option: KerberosOrLocalPasswd
/usr/local/etc/sshd_config: line 70: Bad configuration option: KerberosTicketCleanup
/usr/local/etc/sshd_config: line 74: Bad configuration option: AFSTokenPassing
/usr/local/etc/sshd_config: line 77: Bad configuration option: KerberosTgtPassing
/usr/local/etc/sshd_config: terminating, 5 bad configuration options

Experimentation reveals that these are the only options that sshd does not
recognize.  ssh does not like these configuration options, either:

/usr/local/etc/ssh_config: line 20: Bad configuration option: AFSTokenPassing
/usr/local/etc/ssh_config: line 38: Bad configuration option: KerberosAuthentication
/usr/local/etc/ssh_config: line 39: Bad configuration option: KerberosTgtPassing
/usr/local/etc/ssh_config: terminating, 3 bad configuration options

I don't have the facilities to test whether or not Kerberos or AFS are actually
working.