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

Verified that arm builds locally.

BUG=none
TBR=jkummerow@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/306473004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21512 ce2b1a6d-e550-0410-aec6-3dcde31c8c00