dbus-run-session starts a dbus-daemon before the client application.
We must avoid letting the application try to connect before the
dbus-daemon's DBusServer is listening for connections.

In the Unix implementation, we already achieved this via the
--print-address option. If the client tried to connect too soon,
the server would not yet be listening and the client would fail.

In the Windows implementation, we communicate the bus address to
the client application as an autolaunch: address, so if the client
tried to connect too soon, it would autolaunch a new dbus-daemon
instead of using the one that it was intended to use.

We can avoid this by using a new option to pass in a Windows event
object, which will be set when the server has started and is ready
to process connections.

Fixes #297