Three integer algorithms drawing circles

Midpoint and two versions of Bresenham algorithm for drawing circle.

bresenham_circle => code by CHANDAN KUMAR modified to work as a function, returning X and Y coordinates of circle point with zero origin

bresenham_circle2 => algorithm from Wikipedia (http://en.wikipedia.org/wiki/Midpoint_circle_algorithm)

midpoint_circle => midpoint algorithm from http://groups.csail.mit.edu/graphics/classes/6.837/F98/Lecture6/circle.html

circle_test => explains why i had to look for the third algorithm, and the first two were not good enough :)