[Bug-gsl] bugs when using gsl_sf_hyperg_U

[Feng Gao]

Hi,

I have been using the gsl_sf_hyperg_U function for a while and I found
several bugs when calculating normal values. For example,

1) gsl_sf_hyperg_U(1, -500, 0.1) gives incorrect value: 9.3246e+03, which
actually should be around 0.19.

2) Many domain error bugs. For example, gsl_sf_hyperg_U(1, -6.67, 1) should
have value ~0.128 but will invoke domain error for gsl.

Hope that you can further investigate this and come up with solutions.
Thanks!

Best Regards,

Feng