%N errfun %F $MIR/src/subs/gamma.for
%D Find Erf(x)
%P nebk
%: error function, gamma function, utilities
%B
      real function errfun (x)

      implicit none
      real x

 Find Erf(x) from Gamma function
 Algorithm from Numerical Recipes p 164

  Input
    x     r     Argument
