Let rounded rectangles be antialiased by default

This was the behavior in Qt Quick 1.1, so we should keep it

Change-Id: I5c6968225e20b06f550c52741fff571088b0100b
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

src/quick/items/qquickrectangle.cpp

@@ -475,7 +475,7 @@ QSGNode *QQuickRectangle::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData
     }
 
     rectangle->setRadius(d->radius);
-    rectangle->setAntialiasing(d->antialiasing);
+    rectangle->setAntialiasing(d->antialiasing || d->radius > 0);
 
     QGradientStops stops;
     if (d->gradient) {