[Bug-gsl] GSL special functions

[Harald Moseby]

I have noticed a few anomalies in a few special funtions of GSL:

1) Both gsl_sf_zeta_int() and gsl_sf_zetam1_int() return zero at even 
negative integers. gsl_sf_zetam1_int_e() should be modified.

2) gsl_sf_laguerre_n(10000001, 2.5, 2.5) returns a wrong answer; -1.5e6 
insted of 1.5e6. laguerre_large_n() seems to return the correct answer 
only when n is even. Multiply by -1 when n is odd? I don't know.

3) gsl_sf_hyperg_1F1(1.2, 1.1e-15, 1.5) returns a wrong answer. 
hyperg_1F1_renorm_b0() seems incorrect. I have not been able to understand 
the implementation of Abramowitz+Stegun 13.3.7.

4) hyperg_1F1_large2bm4a() does not give correct answers. The algorithm is 
implemented correctly, but fails it's task when a in [-1, 1]. It seems to 
me that a must be large negative for hyperg_1F1_large2bm4a() to produce 
sensible results.

Harald Moseby,
Oslo