This detects when it is running as pid 1, and becomes an init process.
Specifically this means handling SIGCHLD and reaping processes
(otherwise they become zombies) and forwarding signals to "real"
process.
We fork and re-exec ourselves so that we only get *this* SIGCHLD for
orphaned processes (re-parented to 1) and not the real events from
running things like git or ssh.
Tim Hockin