use compare nil ic only for non-strict equality. strict-equality only has one check and cannot deopt. should therefore not be part of the stub.

BUG=
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/16732002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15045 ce2b1a6d-e550-0410-aec6-3dcde31c8c00