Map::Hash() calculation made deterministic in predictable mode.

BUG=v8:3563
LOG=N
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/610363002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24281 ce2b1a6d-e550-0410-aec6-3dcde31c8c00