Remove elements transitions from the transition array.

This is preparatory work for reordering the transition tree. Since elements transitions will be at the root of the transition tree, runtime access to them is slow since we have to walk the transition tree backwards first. Hence remove the optimization that promoted them to a special field, requiring a pointer (mostly NULL) in every non-simple transition array.

R=titzer@chromium.org

Review URL: https://chromiumcodereview.appspot.com/21228002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15993 ce2b1a6d-e550-0410-aec6-3dcde31c8c00