0.8.6.19:

0.8.6.19:
	Fix for CONS.SUBTYPEP.xx from PFD's test suite
	... more work in the CONS union method.

	                      ALERT ALERT ALERT

	this change reportedly makes PFD's random tester crawl, slowing it
	by a factor of 15 on input terms (type specifiers) of size 50.
	Options include
	  * ignoring this;
	  * having a cutoff in time or complexity beyond which we return
	    NIL, NIL;
	  * optimizing (NOT <cons>) some more;
	  * ...
	but at least it's slightly more correct now.