Hello: example fix travis warning

missing function declaration
implicit cast
some style fix

Tools/Hello/Hello.cpp

@@ -5,17 +5,20 @@
 
 #include <AP_HAL/AP_HAL.h>
 
+void setup();
+void loop();
+
 const AP_HAL::HAL& hal = AP_HAL::get_HAL();
 
 void setup()
 {
-	hal.console->printf("hello world\n");
+    hal.console->printf("hello world\n");
 }
 
 void loop()
 {
-	hal.scheduler->delay(1000);
+    hal.scheduler->delay(1000);
-	hal.console->printf("*\n");
+    hal.console->printf("*\n");
 }
 
 AP_HAL_MAIN();