AArch64: Added arm64 quick backend as an arm clone.

Created a new directory arm64 under compiler/dex/quick which contains
a copy of the 32-bit arm backend.  In following CLs, this code will
be replaced/modified to support Aarch64.

Change-Id: I06c468db8d588e339eecf4d7d85276d5e334a17a
9 files changed