0.8.9.18

0.8.9.18
	Some cosmetic cleanups to make this a better place to start a
	new x86-64 branch

	... remove large chunks of long-float: it didn't work anyway

	... parms.lisp happens fractionally earlier so that we can
	defconstant nil-value slightly more cleanly

	some raw 3s and 4s get made into functions of n-lowtag-bits