Make it pass the Hello handling test including all OOM codepaths.
	Now to do other messages...

	* bus/services.c (bus_service_remove_owner): fix crash when
	removing owner from an empty list of owners
	(bus_registry_ensure): don't leave service in the list of
	a connection's owned services if we fail to put the service
	in the hash table.

	* bus/connection.c (bus_connection_preallocate_oom_error): set
	error flag on the OOM error.

	* dbus/dbus-connection.c (_dbus_connection_new_for_transport):
	handle _dbus_transport_set_connection failure

	* dbus/dbus-transport-unix.c (_dbus_transport_new_for_fd): modify
	to create watches up front and simply enable/disable them as
	needed.
	(unix_connection_set): this can now fail on OOM

	* dbus/dbus-timeout.c, dbus/dbus-watch.c: add concept
	of enabling/disabling a watch or timeout.

	* bus/loop.c (bus_loop_iterate): don't touch disabled
	watches/timeouts

	* glib/dbus-gmain.c: adapt to enable/disable watches and timeouts