说明：  基于三次埃尔米特多项式推导出来的三次样条插值matlab程序，用于知道一阶导数边界条件的插值，不仅可以输出插值节点的值，还可以输出每一段的插值多项式，更重要的是还可以输出各插值点的一阶导数值。
(This is a matlab code of cubic spline interpolation, which is derived the Hermite of three polynomials. It can be used only when the first derivative of boundaries is known. This code can not only output the value of the interpolation node, it can also output every interpolation polynomial, more importantly, it is also can output the first derivative of each interpolation point.)