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Wow, you plowed through a lot of code!

Two sets of optimizations look worthwhile, the memsets() 
and the XINCREFs to INCREFS.

Probably the fastlocals substitutions should be done also, 
but more for beauty and clarity than speed.

I checked those three categories of changes on my 
machine.  They compile fine, pass the standard regression 
tests and checkout okay on my personal, realcode 
testfarm.

I don't think the PyInt_Init() addition buys us anything.  
The register and macro tweaks may cost more in review 
time and potential errors than they could ever save in 
cumulative computer time.

Recommend you get these in before someone changes the 
codebase.