[packagekit] Cancel method for dbus backends

[Richard Hughes]

On Thu, 2008-02-28 at 00:45 +0100, Richard Hughes wrote:
> I guess DBUS is serializing the method calls, which isn't insane. DBUS
> legends: is there away to abort a async dbus method call from the
> caller? What about dbus_g_proxy_end_call or dbus_g_proxy_cancel_call?

I've added up to 49e2e0b85cfb1ec3c72e020597a2e15db72c4e5a for you to
play with - it's totally untested as it's waaaay past my bedtime.

Richard.