Handle misaligned loads and stores in load elimination. Do not track misaligned loads and be conservative about invalidating misaligned stores. Add more tests for number conversion to string (NumberToStringStub exhibits misaligned loads)

BUG=v8:2934
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/28383003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17294 ce2b1a6d-e550-0410-aec6-3dcde31c8c00