Merged r19798, r19896 into 3.23 branch.

Fix bug in constant folding object comparisons.

Correctly retain argument value when deopting from Math.round on x64.

BUG=351624
LOG=N
R=machenbach@chromium.org

Review URL: https://codereview.chromium.org/196383025

git-svn-id: https://v8.googlecode.com/svn/branches/3.23@19974 ce2b1a6d-e550-0410-aec6-3dcde31c8c00