Bessel function under/overflow near the origin - esp float.

Look at the results of test_bessel, test_sph_bessel, near the originas a function of.
You have to widen the near zero. Look at the near zero asymptotics and come up with a thing
as a function of underflow exponent and nu.
Neumann and K are just going to blow.
Should I go ahead and let J, I return denormal results? Why not.
And if the type doesn't do denorm just zero then and don't sweat.