Add support for a few NEON and ARM SIMD instructions and use them for various
memcpy operations.

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/17858002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15602 ce2b1a6d-e550-0410-aec6-3dcde31c8c00