SITL: Frame and Motor changes to allow motor example

libraries/SITL/SIM_Frame.h

@@ -152,6 +152,9 @@ protected:
     void load_frame_params(const char *model_json);
 #endif
 
+    // get air density in kg/m^3
+    float get_air_density(float alt_amsl) const;
+
     struct Model model;
 
 private:
@@ -163,9 +166,6 @@ private:
     Battery *battery;
 #endif
 
-    // get air density in kg/m^3
-    float get_air_density(float alt_amsl) const;
-
     // json parsing helpers
 #if USE_PICOJSON
     void parse_float(picojson::value val, const char* label, float &param);

libraries/SITL/SIM_Motor.h

@@ -18,8 +18,8 @@
 
 #pragma once
 
-#include "SIM_Aircraft.h"
 #include <AP_Math/AP_Math.h>
+#include <SITL/SITL_Input.h>
 
 namespace SITL {