3 integer algorithms for drawing circles

3 implementations of Bresenham and Midpoint algorithm.

All return X and Y values of point coordinates with given radius and zeros center.

R=7;
[X1,Y1]=midpoint_circle(R);
[X2,Y2]=bresenham_circle(R);
[X3,Y3]=bresenham_circle2(R);

See circle_test.m for examples.