Implement simplistic local alias analysis, which will be used in both check elimination and load elimination.

BUG=
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/23516010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16645 ce2b1a6d-e550-0410-aec6-3dcde31c8c00