Reland of r19102: Check elimination improvement: propagation of state through phis is supported, CheckMap narrowing implemented with tests.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/146623006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19229 ce2b1a6d-e550-0410-aec6-3dcde31c8c00