/*
 * 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) {