The optimization is not correct for unsigned output types, and we the
overall complexity seems too high. We need to find a better way to
take into account the input/output type restrictions.

Also added a regression test for the unsigned output bug.

BUG=v8:5267,v8:5270,v8:5357
TBR=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2320013002
Cr-Commit-Position: refs/heads/master@{#39262}