x86 update

[Matthew Fluet]

> > Have you run the full set of regressions with -native-live-transfer
> > true?  I didn't.
> 
> I had with the new-codegen/old-precodegen combination.  I'll try with the
> new/new combination.

Not problem on the regression suite.  I should have tried the
benchmarks next, but I figured I would try the self-compile.
Unfortunately, all those traceCalls in the x86backend add up and I ran out
of disk space for the log before I hit the memory explosion.  I'll try it
again with just a traceCall on the computeLiveTransfer function.