Function: besselk
Section: transcendental
C-Name: kbessel0
Prototype: GGD0,L,p
Help: besselk(nu,x,{flag=0}): K-bessel function of index nu and argument x
 (x positive real of type real, nu of any scalar type). flag is optional, and
 may be set to 0: default; 1: use hyperu

