Fix DeferredTaggedToINoSSE2 to not unconditionally untag undefined to 0.

R=danno@chromium.org

Review URL: https://chromiumcodereview.appspot.com/16228002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14896 ce2b1a6d-e550-0410-aec6-3dcde31c8c00