sse4.1: PPC AltiVec has no vec_splat_s64
sse4.1: PPC AltiVec has no vec_splat_s64

Replace vec_splat_s64(0) with vec_splats(HEDLEY_STATIC_CAST(signed long long, 0))

nemequ/simde,nemequ/simde,nemequ/simde