/*
* Fill an ellipse at the specified coordinates with the given color
*
* Examples:
* # fill an ellipse in the center of the image using the context color
* xc, yc, w, h = image.w / 2, image.h / 2, image.w / 2, image.h / 2
* image.draw_oval xc, yc, w, h
*
* # fill a violet circle in the center of the image
* rect = [image.w / 2, image.h / 2, image.w / 2, image.w / 2]
* color = Imlib2::Color::VIOLET
* image.draw_ellipse rect, color
*
*/
static VALUE image_fill_ellipse(int argc, VALUE *argv, VALUE self) {