Partially fix underspecification of saturating narrowing primops that
became apparent whilst looking into the problem of implementing the
SSE4 packusdw instruction.  Probably breaks Altivec.



git-svn-id: svn://svn.valgrind.org/vex/trunk@2159 8f6e269a-dfd6-0310-a8e1-e2731360e62c
11 files changed