Mark Dickinson :
> So a full patch for this should touch at least Python/pymath.c, 
> Modules/mathmodule.c, configure.in, Lib/test/test_math.py, and 
> Doc/Library/math.rst.
here are patches for Python/pymath.c, Modules/mathmodule.c,
Lib/test/test_math.py, Doc/Library/math.rst and also Include/pymath.h.
i haven't touched configure.in as i've erf, erfc, lgamma and tgamma
on my platform, so the patches can be tested.
the doc may need better wording and test_math.py some additionnal tests.

Raymond Hettinger:
> It would be nice if we knew the error bounds for each of the 
> approximation methods. Do we know how the coefficients were generated?
it will be really great if we're able to regenerate all these
coefficients. this may be done by following the comments in
the original codes, but not that easy and not sure one will obtain
the same things.

> The lowword/highword macros look to be tightly tied to the internal 
> processor representation for floats.  It would be more portable and 
> maintainable to replace that bit twiddling with something based on frexp
it seems possible to avoid the use of these macros.
i'll try to find time to dig up these possibilities.