Given a list of 2-d points defining the vertices of a polygon, determine whether these points are sorted clockwise.
The inputs to this function are two vectors x and y (with equal size) containing the x- and y- coordinates of the polygon vertices, respectively.
The function should return true when sorted clockwise, and false when sorted counterclockwise (the polygon vertices will always be sorted either way).
x = [-1,-1,1,1]; y = [-1,1,1,-1];
defines a square, the vertices are listed clockwise
d_correct = true;