黄金分割法（0.618）程序，以及进退法选择优化区间-Golden section method (0.618) procedures

黄金分割法求极小，返回值fm为函数极小值，tm为极小值点，f为给定函数，t为函数变量，[a,b]为变量t的搜索区间-Golden section method is extremely small, the return value for the function fm minimum, tm for the minimum point, f for a given function, t for the function of variables, [a, b] for variable s