Phase 4 support for IBM Power ISA 2.07

This patch adds support for the following instructions for doing
various arithmetic, logic, and load/store VSX operations:

  xscvsxdsp xscvuxdsp xsaddsp xssubsp xsdivsp xsmaddasp xsmaddmsp
  xsmsubasp xsmsubmsp xsnmaddasp xsnmaddmsp xsnmsubasp xsnmsubmsp
  xsmulsp xssqrtsp xsresp xsrsqrtesp xsrsp xxlorc xxlnand xxleqv
  lxsiwzx lxsiwax lxsspx stxsiwx stxsspx

Signed-off-by: Maynard Johnson <maynardj@us.ibm.com>

Bugzilla 325477


git-svn-id: svn://svn.valgrind.org/vex/trunk@2781 8f6e269a-dfd6-0310-a8e1-e2731360e62c