This eliminates a large amount of hand-written assembly in the platforms.

BUG=
R=danno@chromium.org, mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/16453002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15328 ce2b1a6d-e550-0410-aec6-3dcde31c8c00