[Backport] Fix clang++ warnings on -Wtautological-constant-out-of-range-compare

BUG=v8:3730
LOG=N
R=dslomov@chromium.org

Review URL: https://codereview.chromium.org/750093003

Cr-Commit-Position: refs/heads/master@{#25579}
Merge pull request #64 from halton/out-of-range-compare

Fix compiler error on -Wtautological-constant-out-of-range-compare