ArduCopter: add option to disable relay and servorelay libraries

ArduCopter/Copter.cpp

@@ -178,7 +178,9 @@ const AP_Scheduler::Task Copter::scheduler_tasks[] = {
     SCHED_TASK_CLASS(AC_Sprayer,           &copter.sprayer,               update,         3,  90,  54),
 #endif
     SCHED_TASK(three_hz_loop,          3,     75, 57),
+#if AP_SERVORELAYEVENTS_ENABLED
     SCHED_TASK_CLASS(AP_ServoRelayEvents,  &copter.ServoRelayEvents,      update_events, 50,  75,  60),
+#endif
     SCHED_TASK_CLASS(AP_Baro,              &copter.barometer,             accumulate,    50,  90,  63),
 #if AC_PRECLAND_ENABLED
     SCHED_TASK(update_precland,      400,     50,  69),

ArduCopter/Parameters.cpp

@@ -449,9 +449,11 @@ const AP_Param::Info Copter::var_info[] = {
     GOBJECT(camera, "CAM", AP_Camera),
 #endif
 
+#if AP_RELAY_ENABLED
     // @Group: RELAY_
     // @Path: ../libraries/AP_Relay/AP_Relay.cpp
     GOBJECT(relay,                  "RELAY_", AP_Relay),
+#endif
 
 #if PARACHUTE == ENABLED
     // @Group: CHUTE_

ArduCopter/system.cpp

@@ -92,7 +92,9 @@ void Copter::init_ardupilot()
     // motors initialised so parameters can be sent
     ap.initialised_params = true;
 
+#if AP_RELAY_ENABLED
     relay.init();
+#endif
 
     /*
      *  setup the 'main loop is dead' check. Note that this relies on