Integrate Doc Ok's tracking

[nitsch]

@thp If you feel like bringing even more improvements to the library, maybe you are interested in integrating Doc Ok's tracking which is a rather simple but very robust algorithm with excellent results.

[cboulay]

I think this is a faithful reproduction in C++, but it's been a long time so I can't remember if it was finished or not.

Also, immediately above that function is another implementation that I wrote that uses trigonometry and similar triangles to find a direct solution and is quite fast, but is less robust to noise.