AP_Soaring: remove use of AP_AHRS from most headers

don't need to know the details, just that it is a class

libraries/AP_Soaring/AP_Soaring.cpp

@@ -2,6 +2,7 @@
 
 #if HAL_SOARING_ENABLED
 
+#include <AP_AHRS/AP_AHRS.h>
 #include <AP_Logger/AP_Logger.h>
 #include <AP_TECS/AP_TECS.h>
 #include <GCS_MAVLink/GCS.h>

libraries/AP_Soaring/Variometer.cpp

@@ -4,6 +4,7 @@ Manages the estimation of aircraft total energy, drag and vertical air velocity.
 */
 #include "Variometer.h"
 
+#include <AP_AHRS/AP_AHRS.h>
 #include <AP_Logger/AP_Logger.h>
 
 Variometer::Variometer(const AP_FixedWing &parms, const PolarParams &polarParams) :

libraries/AP_Soaring/Variometer.h

@@ -5,10 +5,11 @@ Manages the estimation of aircraft total energy, drag and vertical air velocity.
 */
 #pragma once
 
-#include <AP_AHRS/AP_AHRS.h>
 #include <AP_Param/AP_Param.h>
 #include <Filter/AverageFilter.h>
+#include <Filter/LowPassFilter.h>
 #include <AP_Vehicle/AP_FixedWing.h>
+#include <AP_Common/Location.h>
 
 class Variometer {