Also several bugs with Smi/double elements handling and make Ensure* routines more flexible.

BUG=none
TEST=test/mjsunit/array-construct-transition.js

Review URL: http://codereview.chromium.org/8820014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10218 ce2b1a6d-e550-0410-aec6-3dcde31c8c00