Fix implementation of compare-minus-zero-and-branch on ia32 and x64.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/63573004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17657 ce2b1a6d-e550-0410-aec6-3dcde31c8c00