Fix algebraic simplification for Iop_AndV256.


git-svn-id: svn://svn.valgrind.org/vex@2902 8f6e269a-dfd6-0310-a8e1-e2731360e62c
Comment out an unsed function to avoid a compiler warning.


git-svn-id: svn://svn.valgrind.org/vex@2903 8f6e269a-dfd6-0310-a8e1-e2731360e62c