Add support for Float32 representation changes.

R=bmeurer@chromium.org
BUG=v8:3589
LOG=n

Review URL: https://codereview.chromium.org/598963002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24180 ce2b1a6d-e550-0410-aec6-3dcde31c8c00