Rolling v8/tools/clang to a56c9063d582660d29b32f967ce20875c589fc3e

TBR=machenbach@chromium.org,vogelheim@chromium.org,hablich@chromium.org

Review URL: https://codereview.chromium.org/1407453002

Cr-Commit-Position: refs/heads/master@{#31223}