Oversize bitfields

[Jim Dehnert]

I updated the oversize bitfield description, in the process moving it
to the main class allocation description and including a description
on non-oversize bitfield allocation.  Please take a look (it's red),
especially Mark, and let me know if it is clearer.

(The updates I've described today are in HTML, not yet in the PDF.)

Jim
-	    Jim Dehnert		dehnert at sgi.com
				(650)933-4272