Support x87-only platform (ia32 without SSE)

R=danno@chromium.org

Review URL: https://codereview.chromium.org/293743005

Patch from Weiliang Lin <weiliang.lin@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21469 ce2b1a6d-e550-0410-aec6-3dcde31c8c00