constant switch test bug in x86Translate

[Stephen Weeks]

> This was causing problems with the self-compile because I am migrating from
> lists to vectors for the CPS IL.  Anyways, after fixing the bug, I attempted a
> self compile, which produced G1, which got a segfault when processing the basis
> library.  I decided that I'm in a weird enough state that it's worth rerunning
> the regressions, and indeed, many of them failed.  The only two changes since I
> ran the regressions are my bug fix (a couple of lines in constant propagation)
> and the codegen changes you sent today, so I'm betting on the codegen.  I put a
> snapshot at http://www.star-lab.com/sweeks/src.tgz.  I'm now backing out the
> codegen to the one from last night and trying again.  I'll report shortly.

All the regressions passed with the new constant propagation and the codegen I
had from last night, so I'm guessing there's something wrong with the changes
you sent today.