@midpointcirle: added test and demo
@midpointcirle: added test and demo

It turns out that calling repetitally next() to get the whole circle is
really slow (1000 times slower than using trigonomotric functions). So
we have to come up with something.
Signed-off-by: Jean-Yves Tinevez <17c1793fcc6179ec3ae6319887e209161427f317@gmail.com>

tinevez/jyt-matlab,tinevez/jyt-matlab,tinevez/jyt-matlab,tinevez/jyt-matlab,tinevez/jyt-matlab