ARM64: Fix Register and FPRegister copy constructors.

This issue was introduced in r19156.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/207743003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20212 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
ARM64: Prevent compilers to optimize away NaN negation in tests.

BUG=v8:3226
R=ulan@chromium.org, jochen@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/196173021

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20213 ce2b1a6d-e550-0410-aec6-3dcde31c8c00