Simulator rewrite

[xoft]

I think rev 1227 is about as much as I'll be touching the redstone simulator. I'll be adding a new function, SimulateInChunk(), to the other simulators; a simulator can decide whether it wants the old-style global simulation function or the new-style per-chunk simulation function; the redstone simulator seems too complicated for me to convert at this moment.

So you can wait for a bit longer if you want to see how that will turn out, or you can start tinkering with the redstone sim rightaway