0.6.11.21:

0.6.11.21:
	fixed T-to-AT typo in DEFUN LISTEN
	made CROSS-TYPEP understand SATISFIES types
	rewrote the TYPE-UNION method :SIMPLE-INTERSECTION2 (and
		:COMPLEX-INTERSECTION2) to return UNION-TYPE when
		that's simpler than the result of just punting; now
		bug 89 is fixed, (AND KEYWORD (OR KEYWORD NULL)=KEYWORD