Review Request: Workaround for non-thread-safety of QDBusConnection

[Maksim Orlovich]

>
> In QtDBus binding a call to
> dbus_set_api_policy(DBUS_API_POLICY_NON_THREAD_SAFETY_FIX,1)  would
> activate this specific fix

It's possible for a process to use more than one toolkit at once.
(For example, in Netscape plugin support implementations with a Qt-based
host)