Add wheelMouse() to reference

core/src/processing/core/PApplet.java

@@ -3069,10 +3069,19 @@ public class PApplet extends Applet
     mouseExited();
   }
 
-
+  /**
+   * @nowebref
+   */
   public void mouseWheel() { }
 
-
+  /**
+   * The event.getAmount() method returns negative values if the mouse wheel 
+   * if rotated up or away from the user and positive in the other direction. 
+   * On OS X with "natural" scrolling enabled, the values are opposite.
+   *
+   * @webref input:mouse
+   * @param event the MouseEvent
+   */
   public void mouseWheel(MouseEvent event) {
     mouseWheel();
   }