#28 hspo_SN_construct_eqn:94: replace call to ezDFDX

[Frank Schilder]

For numerical stability, the call to exDFDX should be replaced with numerical differentiation with larger step size to avoid aliasing effect of cascaded FDM.

Long-term goal: provide explicit derivative.

[Frank Schilder]

The relevant code fragment is:

if nargout>=3
  [data, Jpx] = coco_ezDFDX('f(o,d,x)', prob, data, ...
    @(o,d,u) temp(o,d,u,w), [p; x]);
  J = [Jpx, -sn.cont, Px; sn.zrs1, 2*v(sn.sidx{1})', sn.zrs2];
end