Enforce cases have no duplicates.
Enforce cases have a maximum range of 2^31.
Enforce default case comes last.

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

Review URL: https://codereview.chromium.org/1578963003

Cr-Commit-Position: refs/heads/master@{#33221}