Floating point rounding modes: we should restrict them slightly

[Jason House]

Don Wrote:
> 
> I've provided very simple solutions for both of these. I'm getting 
> pretty irritated that people are acting as though these are difficult 
> problems and trying to come up with convoluted solutions. Impose minimal 
> semantics and it becomes trivial.

FWIW, I've liked your proposals, but I don't feel qualified to comment. I never adjust rounding modes. I do like how I can be ignorant and get code that is better optimized. You've shown deep knowledge of floating point operation in the past, and I'm inclined to accept reasonable-sounding proposals from those that know way more than me.