We now pick up all the user's extra GIDs from /etc/group and make
sure those are set before exec'ing a service.
This means we finally get to enjoy being in more than one group. :^)
For services explicitly configured as lazy, SystemServer will now listen
on the socket and only spawn the service once a client attempts to connect
to the socket.
SystemServer can now create sockets on behalf of services before spawning any
of them, and pass the open socket fd as fd 3. CLocalServer gains a method to
complete the takeover and listen on the passed fd.
This is not used by any services at the moment.
When reaping a child, SystemServer will now match up child's pid with its own
record of the services, and respawn the service if keepalive is enabled for it.
For example, we want to restart the WindowServer if it crashes, but we wouldn't
want to restart the Terminal if it gets closed.
