ssh-keysign(8) on OpenBSD

The text 5acb2434af17, as OpenBSD 6.6, OpenBSD 6.5, OpenBSD 6.4, OpenBSD 6.3, OpenBSD 6.2, OpenBSD 6.1, OpenBSD 6.0, OpenBSD 5.9 shipped it.

ssh helper program for host-based authentication