You can now ask SystemServer to not only listen for connections on the socket,
but to actually accept them, and to spawn an instance of the service for each
client connection. In this case, it's the accepted, not listening, socket that
the service processes will receive using socket takeover.
This mode obviously requires the service to be a multi-instance service.
For this kind of services, there's no single PID of a running instance;
there may be multiple, or no instances of the service running at any time.
No keepalive functionality is available in this mode, since "alive" doesn't
make sense for multi-instance services.
At the moment, there's no way to actually create multiple instances of
a service; this is going to be added in the next commit.
* In some cases, we can first call sigaction()/signal(), then *not* pledge
sigaction.
* In other cases, we pledge sigaction at first, call sigaction()/signal()
second, then pledge again, this time without sigaction.
* In yet other cases, we keep the sigaction pledge. I suppose these could all be
migrated to drop it or not pledge it at all, if somebody is interested in
doing that.
It didn't feel right to have a "DHCPClient" in a "Servers" directory.
Rename this to Services to better reflect the type of programs we'll
be putting in there.
