Consider rational bezier curves instead of bezier curves

[carewolf]

Rational bezier curves are curves where the control point(s) has an extra weight.
There are two stong benefit of rational bezier curves over basic bezier curves:
a) They can represent conic arcs and thus circles accurately. This makes arc a special case of bezier curves, and possible to represent it internally as a single bezier curve.
b) They are stable under projection transformation. You do not currently have 3D transforms in the library, but if you had, then bezier curves would be broken by them, and need to split or rasterized after a projection transform, but rational bezier curves can be transformed under any 3D transform and still be a rational bezier curve.