Function: plotarc
Section: graphic
C-Name: plotarc
Prototype: vLGGD0,L,
Help: plotarc(w,x2,y2,{filled=0}): if the cursor is at position (x1,y1), draws the
 ellipse that fits inside the box with diagonal (x1,y1) and (x2,y2) in rectwindow w
 (cursor does not move).
 If filled=1, fill the ellipse
Doc: let $(x1,y1)$ be the current position of the virtual cursor. Draws in the
 rectwindow $w$ the outline of the ellipse that fits inside the box such that the points
 $(x1,y1)$ and $(x2,y2)$ are opposite corners. The virtual cursor does \emph{not} move.
 If $\var{filled}=1$, fills the ellipse.
 \bprog
 ? plotinit(1);plotmove(1,0,0);
 ? plotarc(1,50,50); plotdraw([1,100,100]);
 @eprog
