This patch includes the following changes.
     1, Enable the turbofan backend support for X87 platform. It depends on previous CL: 3fdfebd2.
     2, Enable the test cases which are disabled because turbofan for X87 was not enabled.

BUG=v8:4135
LOG=N

Review URL: https://codereview.chromium.org/1179763004

Cr-Commit-Position: refs/heads/master@{#29049}

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/499563007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23342 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/323413002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21785 ce2b1a6d-e550-0410-aec6-3dcde31c8c00