Hello: added a trivial test sketch

works with APM1/APM2/SITL

Tools/Hello/Hello.pde

@@ -0,0 +1,37 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
+
+/*
+  simple hello world sketch
+  Andrew Tridgell September 2011
+*/
+
+#include <AP_Common.h>
+#include <AP_Progmem.h>
+#include <AP_HAL.h>
+#include <AP_HAL_AVR.h>
+#include <AP_HAL_AVR_SITL.h>
+#include <AP_HAL_Empty.h>
+#include <AP_Math.h>
+#include <Filter.h>
+#include <AP_InertialSensor.h>
+#include <AP_ADC.h>
+#include <GCS_MAVLink.h>
+#include <AP_Param.h>
+#include <AP_Baro.h>
+#include <AP_Compass.h>
+#include <AP_Declination.h>
+#include <SITL.h>
+
+const AP_HAL::HAL& hal = AP_HAL_BOARD_DRIVER;
+
+void setup() {
+	hal.console->println_P(PSTR("hello world"));
+}
+
+void loop()
+{
+	hal.scheduler->delay(1000);
+	hal.console->println("*");
+}
+
+AP_HAL_MAIN();

Tools/Hello/Makefile

@@ -0,0 +1,4 @@
+#
+# Trivial makefile for building APM
+#
+include ../../mk/Arduino.mk