* dbus/dbus-marshal.c (_dbus_marshal_set_object_id): new function
	(_dbus_marshal_object_id): new
	(_dbus_demarshal_object_id): new
	(_dbus_marshal_get_arg_end_pos): support object ID type, and
	consolidate identical switch cases. Don't conditionalize handling
	of DBUS_TYPE_UINT64, need to handle the type always.
	(_dbus_marshal_validate_arg): consolidate identical cases, and
	handle DBUS_TYPE_OBJECT_ID

	* dbus/dbus-objectid.c: new file with DBusObjectID data type.

	* dbus/dbus-protocol.h: add DBUS_TYPE_OBJECT_ID