wip/autossh 1.4g NetBSD

autossh is a program to start a copy of ssh and monitor it, restarting it as necessary should it die or stop passing traffic. o The idea is from rstunnel (Reliable SSH Tunnel), but implemented in C. o The author's view is that it is not as fiddly as rstunnel to get to work. o Connection monitoring using a loop of port forwardings or a remote echo service. o Backs off on rate of connection attempts when experiencing rapid failures such as connection refused.