NAME
        AreaCircle -- add a circle to areainfo list for areafill.


    SYNOPSIS
        error = (int) AreaCircle( rp,  cx,  cy, radius)
        D0                        A1   D0   D1  D2

        ULONG AreaCircle(struct rastport *, word, word, uword);

    FUNCTION
        Add circle to the vector buffer. It will be drawn to the rastport when
        areaend is executed.

    INPUTS
        rp       - pointer to a rastport structure

        cx, cy   - the coordinates of the center of the desired circle.

        radius   - is the radius of the circle to draw around the centerpoint.

    RESULTS
        0 if no error
        -1 if no space left in vector list

    NOTES
        This function is actually a macro which calls
            AreaEllipse(rp,cx,cy,radius,radius).

    SEE ALSO
        areamove() areadraw() areacircle() initarea() areaend()
        graphics/rastport.h graphics/gfxmacros.h