Remove HLoadElements instruction and replace with use of more general HLoadNamedField. This removes the need for both the hydrogen and lithium instructions and allows both kinds of loads to be GVN'd.

Review URL: https://codereview.chromium.org/14556020

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14542 ce2b1a6d-e550-0410-aec6-3dcde31c8c00