Determines the number of iterations of Newton's method * required to approximate the square root of x within * the given bound. Newton's method starts out by * setting the initial approximate answer to x. * Then in each iteration, answer is replaced by * the quantity (answer + x / answer) / 2.0. * The process stops when the difference between * x and (answer * answer) is strictly less than * the given bound err. The method * returns the number of iterations required. * The given value x must be non-negative.