buglist bug 7258: acosh(0.0) invalid argument to acosh

(1) -> acosh(0.0)

   >> Error detected within library code:
   invalid argument to acosh

(1) -> acosh(0)::Complex Float

   (1)  0.6776263578 0344027125 E -20 + 1.5707963267 948966192 %i
                                                         Type: Complex(Float)