0.9.7.17:

0.9.7.17:
	Document what we've learnt about discriminating functions
	in the internals manual
	... now we depend on dot (graphviz) to draw pretty state
		transition graphs.
	... lots o' text.  I hope it's clear.

	(it would be good to upload this to the web somewhere, in
	order to be the top hit for e.g. "PCL CONSTANT-VALUE" on search
	engines, so that the next person to hit the swamp has a chance
	to get out before it's too late.  Hack the Makefile enough so
	that we can build an html version of an internals manual.)