Merged r14408 into trunk branch.

Fix clang build for x64.

R=yangguo@chromium.org

Review URL: https://chromiumcodereview.appspot.com/14295020

git-svn-id: https://v8.googlecode.com/svn/trunk@14411 ce2b1a6d-e550-0410-aec6-3dcde31c8c00