曲线拟合函数 三个函数，SPLine 调用另外两个。用时候直接调用SPLine函数，入口pList是已知离散点链表，pDestList是生成的点的链表。SM是在两个点中间插入点的数目，continue=0是采样点无规律，要求生成闭合曲线。-Curve fitting function of the three functions, SPLine call the other two. Spline used when a direct call function, the entrance