Power 8 support, phase 5

Power 8 support, phase 5

This commit adds the testcases for the following instructions:

  vpmsumb, vpmsumh, vpmsumw, vpmsumd, vpermxor, vcipher, vcipherlast,
  vncipher, vncipherlast, vsbox,
  vclzb, vclzw, vclzh, vclzd,
  vpopcntb, vpopcnth, vpopcntw, vpopcntd,
  vnand, vorc, veqv,
  vshasigmaw, vshasigmad,
  bcdadd, bcdsub

The VEX commit that added the support for the above instructions was
commit 2789.

The patch is for Bugzilla 325628

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13646