arm64: implement: abs d_d, neg d_d, abs std7_std7, addhn, subhn, raddhn, rsubhn


git-svn-id: svn://svn.valgrind.org/vex@2877 8f6e269a-dfd6-0310-a8e1-e2731360e62c
arm64: implement: addp std7_std7_std7, addv vector, addp d_2d


git-svn-id: svn://svn.valgrind.org/vex@2878 8f6e269a-dfd6-0310-a8e1-e2731360e62c