Adds get_state() and ::state-changed signals, that replace connecting
and ready, as well as providing indication of when the object was closed
or the connection to PulseAudio failed.
https://bugzilla.gnome.org/show_bug.cgi?id=645708
The library is introspected, and should not require using
Pulseaudio directly.
With help from Giovanni Campagna <scampa.giovanni@gmail.com>
(introspection annotations, build fixes)
https://bugzilla.gnome.org/show_bug.cgi?id=629455