[gclist] zillion objects

[Pekka P. Pirinen]

> Sketch of incremental collection:

A good sketch, but you should have mentioned what you left out: That
basically covers the options for the _strong_ tri-colour invariant,
but there is a more subtle alternative, the weak invariant, that
allows using write and read/write barrier techniques with a black
mutator.  Not particularly suitable for a copying collector, though.
I wrote the invariants up for the Reference, for the rest you have
read my paper on barriers (see the Reference for citation).
-- 
Pekka P. Pirinen
Global Graphics Software