Fixing handling of uint32 to be more correct (previously some uint32's
were being interpreted as int32).
Fixing enforcement type matching in comparisons (previously mismatched
expressions could be compared).

BUG= https://code.google.com/p/v8/issues/detail?id=4203
TEST=test-asm-validator
R=titzer@chromium.org,aseemgarg@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1423563008

Cr-Commit-Position: refs/heads/master@{#31726}