Display list jit (comments only)

I have not had much time for this, but this was an initial stab and I thought I'd ask for comments.

It's not any faster and is in many cases slower.  It does have potential and there are a few potential causes for the slowness.  I have not tried ARM yet which may be faster or slower.

Just about everything could be improved.  This is a basic proof of concept.

 * I'm not confident I picked the best regs on x32 (or even x64 I suppose), function calls are so annoying...
 * Invalidation / decimation is pretty weak right now, it should probably remember longer with some form of backoff.
 * Compilation is not that fast but it's not really that slow either.
 * There's some basic slam defense that could probably use more thought / may not even help things.
 * Need to consider how to make it easiest to combine cmds (e.g. VADDR/PRIM/VADDR/PRIM) or reorder even possibly.
 * Need to add an option, off, to enable/disable.  Should be cheapish.  Will rebase this in.
 * Could maybe reduce the onchanged checks or optimize things better.
 * Not sure if better block management (right now just rolling) would be better.

-[Unknown]