Add support for untagged LoadField, StoreField, LoadElement, and StoreElement simplfied operators. This is needed for untagged accesses of typed array backing stores and generally cleans up.

R=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/439223004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22815 ce2b1a6d-e550-0410-aec6-3dcde31c8c00