[vector] binary operations with a scalar

[John Rose]

> On Feb 20, 2018, at 9:19 AM, Paul Sandoz <paul.sandoz at oracle.com> wrote:
> 
> I like this but suggest we keep the code marginally simpler and revisit if we have performance concerns. If we don’t make intrinsic the broadcast+op combination i think something like this is probably ok for now:
> 
>  @Override
>  @ForceInline
>  public Int256Vector add(int o) {
>      return add(Int256Species.broadcastImpl(o));
>  }

That seems like the simplest way, and good to start with, maybe even end with. We could do decisively better with templates but we dint have them yet.