A fast scan line fill. This improves upon other scan fills by determining the the hypotenuse then drawing the scan lines parallel to the hypotenuse. This requires the minimum number of scan lines to fill the triangle.
Unfortunately, scratch doesn't like it when it draw 1px lines at angle other than aligned with the pixels of the screen and so I had to do some strange stuff to remedy that -- Might use this in stamped tri fill v4--
