TF: Lowering representation changes to machine operators (WIP: need inline allocation for some). Move tests related to lowering representation changes into test-changes-lowering.cc.

R=bmeurer@chromium.org, bmeuer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/437583002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22781 ce2b1a6d-e550-0410-aec6-3dcde31c8c00