Evaluates a spline.

s | The spline. |

x | Evaluation point. |

The spline is represented as a matrix(-like object), where each row starts with l.h.s. end-point of the interval, and from the second element on, the polynomial coefficents are defined for the given interval. Technically it needs to be only a piece-wise polynomial, in particular [0 p] is technically a polynomial, where p is a usual polynomial.

```
s =
```*[0, -1; 1, 2,0,0,0,0; 2, -1,0]*;
x0 = *[-1, 0, .5, 1, 1.5, 2, 2.5, 3]*;
xmin = min(x0);
xmax = max(x0);
xeps = (xmax-xmin)/200;
xmin -= 2*xeps;
xmax += 2*xeps;
x = xmin..xeps..xmax;
[! x0; splineEval(s,#x0) !]
plot(x,splineEval(s,#x))