/*
 * Crop an image
 *
 * Examples:
 *   x, y, w, h = 10, 10, image.width - 10, image.height - 10
 *   image.crop! x, y, w, h
 *
 *   rect = [10, 10, image.width - 10, image.height - 10]
 *   image.crop! rect
 *
 *   x, y, w, h = 10, 10, image.width - 10, image.height - 10
 *   image.create_cropped! x, y, w, h
 *
 *   rect = [10, 10, image.width - 10, image.height - 10]
 *   image.create_cropped! rect
 *
 */
static VALUE image_crop_inline(int argc, VALUE *argv, VALUE self) {