Added carrier detect and auto ack enable/disable

RF24.h

@@ -476,6 +476,17 @@ public:
  * will relay these transmissions.
  */
 
+/**
+ * @example scanner.pde 
+ *
+ * Example to detect interference on the various channels available.
+ * This is a good diagnostic tool to check whether you're picking a
+ * good channel for your application.
+ *
+ * Inspired by cpixip.
+ * See http://arduino.cc/forum/index.php/topic,54795.0.html
+ */
+
 /**
  * @mainpage Driver for nRF24L01(+) 2.4GHz Wireless Transceiver
  *