Let's always write "1 << 0", "1 << 1" and so on, except where we need
more than 31 flag bits, where we write "UINT64(1) << 0", and so on to force
64bit values.
This adds a small service "systemd-portabled" and a matching client
"portablectl", which implement the "portable service" concept.
The daemon implements the actual operations, is PolicyKit-enabled and is
activated on demand with exit-on-idle.
Both the daemon and the client are an optional build artifact, enabled
by default rhough.
