* include/vaucanson/z_transducer.hh,
	* include/vaucanson/boolean_transducer.hh: Add AUTOMATON_CONTEXT macro,
	as already done in fmp_transducer and z_fmp_transducer headers.

	* include/vaucanson/contexts/fmp_transducer_functions.thh,
	* include/vaucanson/contexts/fmp_transducer_functions.thxx,
	* include/vaucanson/contexts/transducer_functions.thxx: Modify the
	evaluation functions to give a more user friendly result.