rtiow: don't batch status updates per-line (do per-pixel).

rtiow/src/renderer.rs

@@ -496,7 +496,7 @@ fn render_worker(
             Ok(req) => match req {
                 Request::Line { width, y } => {
                     trace!("tid {} width {} y {}", tid, width, y);
-                    let batch = true;
+                    let batch = false;
                     if batch {
                         let (pixels, rays): (Vec<Vec3>, Vec<usize>) = (0..width)
                             .map(|x| render_pixel(scene, x, y))