Accessibility is not enabled when running as root

The AT-SPI bridge may not initialize when running as root. I noticed this with YaST under SUSE, which, unfortunately, runs its UI as root when configuring anything system-wide. When setting up the dbus connection, we call GetAddress on org.a11y.Bus to get the address for the accessibility bus, but this doesn't work if DBUS_SESSION_BUS_ADDRESS doesn't match the session bus address for the user's ain session. Libatspi tries first to get the bus address from an atom in the X session, and it may be desirable to do this, although it is specific to X11.

Another related issue is that I believe calling ScreenReaderEnabled will return false when running as a user other than the user running the screen reader (ie, root); not sure how best to fix this.