AHRS: removed AHRS_BARO_USE option

this option has caused users too much trouble. The vertical velocity
is too noisy from the baro

libraries/AP_AHRS/AP_AHRS.cpp

@@ -49,12 +49,7 @@ const AP_Param::GroupInfo AP_AHRS::var_info[] PROGMEM = {
     // @Increment: 1
     AP_GROUPINFO("WIND_MAX",  6,    AP_AHRS, _wind_max, 0.0f),
 
-    // @Param: BARO_USE
+    // NOTE: 7 was BARO_USE
-    // @DisplayName: AHRS Use Barometer
-    // @Description: This controls the use of the barometer for vertical acceleration compensation in AHRS. It is currently recommended that you set this value to zero unless you are a developer experimenting with the AHRS system.
-    // @Values: 0:Disabled,1:Enabled
-    // @User: Advanced
-    AP_GROUPINFO("BARO_USE",  7,    AP_AHRS, _baro_use, 0),
 
     // @Param: TRIM_X
     // @DisplayName: AHRS Trim Roll

libraries/AP_AHRS/AP_AHRS.h

@@ -28,8 +28,7 @@ public:
     // Constructor
     AP_AHRS(AP_InertialSensor *ins, GPS *&gps) :
         _ins(ins),
-        _gps(gps),
+        _gps(gps)
-        _barometer(NULL)
     {
         // load default values from var_info table
         AP_Param::setup_object_defaults(this, var_info);
@@ -57,9 +56,6 @@ public:
             _compass->set_board_orientation((enum Rotation)_board_orientation.get());
         }
     }
-    void set_barometer(AP_Baro *barometer) {
-        _barometer = barometer;
-    }
     void set_airspeed(AP_Airspeed *airspeed) {
         _airspeed = airspeed;
     }
@@ -171,7 +167,6 @@ public:
     AP_Float _kp;
     AP_Float gps_gain;
     AP_Int8 _gps_use;
-    AP_Int8 _baro_use;
     AP_Int8 _wind_max;
     AP_Int8 _board_orientation;
 
@@ -195,7 +190,6 @@ protected:
     //       IMU under us without our noticing.
     AP_InertialSensor   *_ins;
     GPS                 *&_gps;
-    AP_Baro             *_barometer;
 
     // a vector to capture the difference between the controller and body frames
     AP_Vector3f         _trim;

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -494,16 +494,6 @@ AP_AHRS_DCM::drift_correction(float deltat)
         _last_airspeed = airspeed.length();
     }
 
-    /*
-     *  The barometer for vertical velocity is only enabled if we got
-     *  at least 5 pressure samples for the reading. This ensures we
-     *  don't use very noisy climb rate data
-     */
-    if (_baro_use && _barometer != NULL && _barometer->get_pressure_samples() >= 5) {
-        // Z velocity is down
-        velocity.z = -_barometer->get_climb_rate();
-    }
-
     // see if this is our first time through - in which case we
     // just setup the start times and return
     if (_ra_sum_start == 0) {