Only activate SSE2 by default on ia32

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/432863002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22779 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
X87: Unify InstanceofStub interface descriptors

port r22755.

original commit message:
  Unify InstanceofStub interface descriptors

BUG=
R=mstarzinger@chromium.org, weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/435603007

Patch from Chunyang Dai <chunyang.dai@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22780 ce2b1a6d-e550-0410-aec6-3dcde31c8c00