Don't call dbus_connection_dispatch recursively

dbus_connection_dispatch is trying to lock the connection when it is
already locked, resulting in a deadlock, so just don't call it
recursively for now.
Don't dispatch while calling get_accessibility_bus_address

Calling dbus_connection_dispatch isn't really needed when fetching the
bus address--this is only done once.
Include config.h in private header

atspi-misc.c was not including config.h anywhere, resulting in HAVE_X11
not being defined, so X would not be queried when fetching the
accessibility bus address.

https://bugzilla.gnome.org/show_bug.cgi?id=707084