AC_WPNav: move AC_Avoidance defines into libraries

libraries/AC_WPNav/AC_Loiter.cpp

@@ -1,6 +1,7 @@
 #include <AP_HAL/AP_HAL.h>
 #include "AC_Loiter.h"
 #include <AP_Vehicle/AP_Vehicle_Type.h>
+#include <AC_Avoidance/AC_Avoid.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -265,7 +266,7 @@ void AC_Loiter::calc_desired_velocity(bool avoidance_on)
         desired_vel.y = desired_vel.y * gnd_speed_limit_cms / horizSpdDem;
     }
 
-#if !APM_BUILD_TYPE(APM_BUILD_ArduPlane)
+#if AP_AVOIDANCE_ENABLED && !APM_BUILD_TYPE(APM_BUILD_ArduPlane)
     if (avoidance_on) {
         // Limit the velocity to prevent fence violations
         // TODO: We need to also limit the _desired_accel

libraries/AC_WPNav/AC_WPNav_OA.cpp

@@ -1,3 +1,7 @@
+#include "AC_WPNav_config.h"
+
+#if AC_WPNAV_OA_ENABLED
+
 #include <AP_Math/control.h>
 #include <AP_InternalError/AP_InternalError.h>
 #include "AC_WPNav_OA.h"
@@ -250,3 +254,5 @@ bool AC_WPNav_OA::update_wpnav()
     // run the non-OA update
     return AC_WPNav::update_wpnav();
 }
+
+#endif  // Ac_WPNAV_OA_ENABLED

libraries/AC_WPNav/AC_WPNav_OA.h

@@ -1,5 +1,9 @@
 #pragma once
 
+#include "AC_WPNav_config.h"
+
+#if AC_WPNAV_OA_ENABLED
+
 #include <AC_WPNav/AC_WPNav.h>
 #include <AC_Avoidance/AP_OAPathPlanner.h>
 #include <AC_Avoidance/AP_OABendyRuler.h>
@@ -45,3 +49,5 @@ protected:
     Location    _oa_destination;        // intermediate destination during avoidance
     Location    _oa_next_destination;   // intermediate next destination during avoidance
 };
+
+#endif  // AC_WPNAV_OA_ENABLED

libraries/AC_WPNav/AC_WPNav_config.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <AC_Avoidance/AC_Avoidance_config.h>
+
+#ifndef AC_WPNAV_OA_ENABLED
+#define AC_WPNAV_OA_ENABLED AP_OAPATHPLANNER_ENABLED
+#endif