* dbus/dbus-message-factory.c (generate_special): modify test to
	avoid using a non-basic dict key

	* dbus/dbus-marshal-validate-util.c: add test for the below

	* doc/dbus-specification.xml: require that dict keys are a basic
	type

	* dbus/dbus-marshal-validate.c
	(_dbus_validate_signature_with_reason): require that dict key is a
	basic type