Salman Haq, could you find out roughly where expm1 starts overflowing on 
your machine?  E.g., do all of the following overflow for you?

>>> from math import expm1
>>> expm1(709.78271289338397)
1.7976931348622732e+308
>>> expm1(709.782712893)
1.797693134172102e+308
>>> expm1(709.7827)
1.7976699566638014e+308
>>> expm1(709.7)
1.6549840276802644e+308

I'm just trying to determine whether the 10.4 expm1 is so broken that 
Python should work around it, or whether it's only slightly broken.  In 
the latter case we can just live with it, and either weaken the tests 
slightly or explicitly skip that particularly test on OS X 10.4.