Revert 21502 - "Move OS::MemCopy and OS::MemMove out of platform to utils"

TBR=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/297303004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21504 ce2b1a6d-e550-0410-aec6-3dcde31c8c00