80 bit reals

[Stephen Weeks]

> > Before the notion of real being 80 bits is frozen into code, I want to do
> > some tests to see how much it will cost us performance-wise (using C).
>
> No worries.  I don't want to muck around with adding new primitive
> datatypes until the SSA->machine->x86 route is running smoothly.

No worries even then, since the only relevant decision is whether Real = Real64
or Real = Real80, which is relatively easy to change.