%N gammln %F $MIR/src/subs/gamma.for
%D Find ln(Gamma(x))
%P nebk
%: gamma function, utilities
%B
      real function gammln(xx)

      implicit none
      real xx

 Find ln(Gamma(x)) where Gamma is the Gamma function
 Algorithm from Numerical Recipes p 157

  Input
    xx     r     Argument
