extend arc to allow ellipse

[Pomax]

arc(x, y, r1, r2, angle, startT, endT, drawWedge) to draw an elliptical arc centered on (x,y) with major/minor radii r1/r2, with the intrinsic ellipse angle angle, starting at T startT and ending at endT (in radians), with drawWedge being the optional boolean flag for drawing a closed wedge rather than an open shape.