Handle Math.log(NaN) correctly in Crankshaft on Intel platforms.

This never worked...

TBR=yangguo@chromium.org

Review URL: https://codereview.chromium.org/118233002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18350 ce2b1a6d-e550-0410-aec6-3dcde31c8c00