ieee.exp tests containing generic FP tests

[Aldy Hernandez]

> Some non-IEEE machines don't just not have NaNs, they also have
> arithmetic that differs in some important way from what the IEEE
> standard specifies.  Tests outside the IEEE directory can't really
> rely on any particular floating-point implementation.
> 
> As far as I can tell, all these tests really won't work on some
> non-IEEE machine.

Bummer.  I guess, it's between XFAILing 90% of the tests on ieee/,
or disabling them entirely (for e500).

'Suppose it won't hurt to disable them.

Thanks Geoff.

Aldy