[ssh-keysign.8 ssh-keysign.c ssh.c ssh_config]
re-enable ssh-keysign's sbit, but make ssh-keysign read
/etc/ssh/ssh_config and exit if HostbasedAuthentication is disabled
globally. based on discussions with deraadt, itojun and sommerfeld;
ok itojun@
[authfile.c authfile.h pathnames.h ssh.c sshconnect.c sshconnect.h
sshconnect1.c sshconnect2.c ssh-keysign.8 ssh-keysign.c Makefile.in]
add /usr/libexec/ssh-keysign: a setuid helper program for hostbased
authentication in protocol v2 (needs to access the hostkeys).
Note: Makefile.in untested. Will test after merge is finished.