[Lightning] release gets closer...

[Paolo Bonzini]

I have merged Ludovic's final implementation of pushr/popr (sorry it 
took so long, I hope you're satisfied with the result) and...

... listen listen, I found a x86-64 host so lightning now passes the 
testsuite there.  Eli, if you want to give a try at integrating the new 
version with mzscheme, I'd be all ears.  I don't have the time right now 
to ensure that GNU Smalltalk's JIT compiler works on x86-64.

Paolo