Activated by the flag --smi-only-arrays

Currently not crankshaft support, using flag on non-ia32 platforms will lead to write barrier misses and crashes.

BUG=none
TEST=elements_kind.js

Review URL: http://codereview.chromium.org/7901016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9392 ce2b1a6d-e550-0410-aec6-3dcde31c8c00