Blender Git Loki

BLI_bitmap_draw_2d: optimize polygon filling

Existing method was fine for basic polygons but didn't scale well
because its was checking all coordinates for every y-pixel.

Heres an optimized version.
Basic logic remains the same this just maintains an ordered list of intersections,
tracking in-out points, to avoid re-computing every row,
this means sorting is only done once when out of order segments are found,
the segments only need to be re-ordered if they cross each other.

Speedup isn't linear, test with full-screen complex lasso gave 11x speedup.