Proposal: fixing the 'pure' floating point problem.

[Walter Bright]

Don wrote:
> That's true, but if you're in a floatingpoint module, and you call a 
> non-floatingpoint module, it's your responsibility to make sure that the 
> rounding mode is back to normal. You're saying that you don't care about 
> the status flags. So it's your own fault if you get surprising results.
> 
> The primary use for adjusting the rounding mode is for things like 
> implementing interval arithmetic. Thus, it's only ever used for small 
> functions.

Perhaps we can go with something simpler. If you call a pure function, 
then the modes must be set to their defaults.