0.8.7.3

0.8.7.3
	Some essential-for-my-comprehension purify and gencgc
	refactoring.  Some functional changes too, though none that
	seem to make any difference in practice

	Ripped out vast swathes of "is this a large object" checking
	in gencgc's allocation routines.  Now the only criterion for
	whether an object is handled as a large object is whether its
	size exceeds the large object threshold.

	Fixed bug in gc_find_freeish_pages that was causing lots of
	fragmentation: allocation regions for small objects may now
	start on the same page as previously closed regions with the
	same characteristics

	Fixed rarely-observed bug in gencgc_pickup_dynamic so that it
	doesn't create a single xMb region from the whole of dynamic
	space when a core is loaded, instead splitting the space into
	as many regions as it can (this may be related to bug 95,
	though I don't /really/ want to claim I fixed that until I see
	better what the problem is there).  Unless you save unpurified
	cores you're unlikely to be bitten by this often.

	New newspace_alloc routine in purify.c makes it all a bit
	easier to see what's going on there.

	Replace all hand-coded memory-copying loops with memcpy(); the
	compiler should be able to optimize this better than we can
	(actually makes no difference that I can detect to execution
	time, but the code is now shorter)