* dbusbind.c: Accept UNIX domain sockets as bus address.

* dbusbind.c: Accept UNIX domain sockets as bus address.
(Fdbus_close_bus): New function.
(Vdbus_registered_buses): New variable.
(xd_initialize): Implement string as bus address.
(Fdbus_init_bus): Add bus to Vdbus_registered_buses).
(Fdbus_get_unique_name, Fdbus_call_method)
(Fdbus_call_method_asynchronously, Fdbus_method_return_internal)
(Fdbus_method_error_internal, Fdbus_send_signal)
(Fdbus_register_signal, Fdbus_register_method): Remove bus type
check.  This is done in xd_initialize_bus.  Adapt doc string, if
necessary.
(xd_pending_messages, xd_read_queued_messages): Loop over buses in
Vdbus_registered_buses.
(Vdbus_registered_objects_table): Create hash.