AnalogSource: added some example code

libraries/AP_AnalogSource/examples/AnalogSource_Arduino/AnalogSource_Arduino.pde

@@ -0,0 +1,41 @@
+// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
+/*
+	Example of AnalogSource Arduino
+*/
+
+#include <FastSerial.h>
+#include <AP_Math.h>
+#include <AP_Common.h>
+#include <Arduino_Mega_ISR_Registry.h>
+#include <AP_PeriodicProcess.h>
+#include <AP_AnalogSource.h>
+
+Arduino_Mega_ISR_Registry isr_registry;
+AP_TimerProcess scheduler;
+
+FastSerialPort0(Serial);
+
+AP_AnalogSource_Arduino vcc_source(ANALOG_PIN_VCC);
+AP_AnalogSource_Arduino pin0(0);
+AP_AnalogSource_Arduino pin1(1);
+
+
+void setup()
+{
+    Serial.begin(115200);
+    isr_registry.init();
+    scheduler.init(&isr_registry);
+    AP_AnalogSource_Arduino::init_timer(&scheduler);
+}
+
+void loop()
+{
+	while (true) {
+		delay(1000);
+		Serial.printf("Vcc: %u PIN0: %u  PIN1: %u  PIN1_avg: %u\n",
+			      (unsigned)vcc_source.read_vcc(),
+			      (unsigned)pin0.read_raw(),
+			      (unsigned)pin1.read_raw(),
+			      (unsigned)pin1.read_average());
+	}
+}

libraries/AP_AnalogSource/examples/AnalogSource_Arduino/Makefile

@@ -0,0 +1,2 @@
+BOARD	=	mega
+include ../../../AP_Common/Arduino.mk