Plane: remove vexing button_update shim

ArduPlane/ArduPlane.cpp

@@ -89,7 +89,7 @@ const AP_Scheduler::Task Plane::scheduler_tasks[] = {
 #endif
     SCHED_TASK_CLASS(AP_InertialSensor, &plane.ins, periodic, 50, 50),
     SCHED_TASK(avoidance_adsb_update,  10,    100),
-    SCHED_TASK(button_update,           5,    100),
+    SCHED_TASK_CLASS(AP_Button, &plane.g2.button, update, 5, 100),
 #if STATS_ENABLED == ENABLED
     SCHED_TASK_CLASS(AP_Stats, &plane.g2.stats, update, 1, 100),
 #endif

ArduPlane/Plane.h

@@ -915,7 +915,6 @@ private:
     void read_rangefinder(void);
     void read_airspeed(void);
     void rpm_update(void);
-    void button_update(void);
     void ice_update(void);
     void init_ardupilot();
     void startup_ground(void);

ArduPlane/sensors.cpp

@@ -104,14 +104,6 @@ void Plane::rpm_update(void)
     }
 }
 
-/*
-  update AP_Button
- */
-void Plane::button_update(void)
-{
-    g2.button.update();
-}
-
 /*
   update AP_ICEngine
  */