Phase 4 support for IBM Power ISA 2.07

This patch adds testcases for the following instructions added 
in phase 4.  The instructions are 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>

VEX commit for the instruction support r2781
Bugzilla 325477


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13611 a5019735-40e9-0310-863c-91ae7b9d1cf9