0.9.7.9:

0.9.7.9:
	Fix bug #392: yet another hole in MAKE-INSTANCES-OBSOLETE
	... make the classoid-based invalidation of layouts clear (set
		to 0) the clos-hash slots of the layout, as well as
		setting depthoid to -1 and layout-invalid to t.
	... this intertwingling is kind of odd, and also kind of
		unnecessary.  Maybe step 1 of an integrated PCL would
		merge layouts and wrappers and centralize their
		handling?
	... fix genesis never to dump layouts with hash-slots of 0.
	... one or two explanatory comments.