Replace NR 2nd deriv + spline interpolation with Graphics Gems V spline.

[stuartjamesmcnicholas]

Replace Numerical Recipes 2nd deriv + spline interpolation with Graphics Gems V spline.

You may or may not find the Graphics Gems Licence more appropriate. If not acceptable, then I guess you reject. :)

[stuartjamesmcnicholas]

Ooops! Do not consider this just yet as it only does 3D. There is a 4D interp (colour) in Coot. I will need to make some changes.

[stuartjamesmcnicholas]

5ffe961

should address the 4th dimension problem.

[pemsley]

Thanks!