blend_image! (Imlib2::Image)

    /*
     * Blend a source image onto the image
     *
     * Examples:
     *   src_x, src_y, src_w, src_h = 10, 10, 100, 100
     *   dst_x, dst_y, dst_w, dst_h = 10, 10, 50, 50
     *   image.blend! source_image,
     *               src_x, src_y, src_w, src_h,
     *               dst_x, dst_y, dst_w, dst_h
     *
     *   src_rect = [50, 50, 5, 5]
     *   dst_rect = [0, 0, image.width, image.height]
     *   merge_alpha = false
     *   image.blend! source_image, src_rect, dst_rect, merge_alpha
     *
     *   src_x, src_y, src_w, src_h = 10, 10, 100, 100
     *   dst_x, dst_y, dst_w, dst_h = 10, 10, 50, 50
     *   image.blend_image! source_image,
     *                      src_x, src_y, src_w, src_h,
     *                      dst_x, dst_y, dst_w, dst_h
     *
     *   src_rect = [50, 50, 5, 5]
     *   dst_rect = [0, 0, image.width, image.height]
     *   merge_alpha = false
     *   image.blend_image! source_image, src_rect, dst_rect, merge_alpha
     *
     */
    static VALUE image_blend_image_inline(int argc, VALUE *argv, VALUE self) {