- Ops: S128Load, S128Store, S128And, S128Or, S128Xor, S128Not, I32x4AddHoriz, I16x8AddHoriz
 - Add x64 assembler support for - phaddd, phaddw, pand, por
 - Enable tests for Globals, other tests applicable to x64 apart from tests for implemented ops

BUG=v8:6020

R=bbudge@chromium.org, bmeurer@chromium.org, zvi.rackover@intel.com

Review-Url: https://codereview.chromium.org/2849463003
Cr-Commit-Position: refs/heads/master@{#45005}