Added %NeverOptimize runtime call that can disable optimizations for a method for tests.

BUG=

Review URL: https://codereview.chromium.org/18214005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15632 ce2b1a6d-e550-0410-aec6-3dcde31c8c00