Use fast_sqrt instead of std::sqrt in simulators.

Use fast_sqrt instead of std::sqrt in simulators.

This prevents clang from inlining and returning inconsistent results.

R=bmeurer@chromium.org
BUG=v8:3802
LOG=N

Review URL: https://codereview.chromium.org/831393006

Cr-Commit-Position: refs/heads/master@{#26158}