complex_csc_real bug?

[G.W.M. Vissers]

Hi,

I think I've found a minor bug in the complex_csc_real function. For 
arguments -1.0 < a < 0,  GSL 1.3 returns

          GSL_SET_COMPLEX (&z, -M_PI_2, -acosh (-1 / a));

I guess that should be

          GSL_SET_COMPLEX (&z, -M_PI_2, acosh (-1 / a));

i.e. the minus sign on the imaginary part should be removed.
Cheers,
Gé