AP_Follow: add and use AP_FOLLOW_ENABLED

libraries/AP_Follow/AP_Follow.cpp

@@ -13,6 +13,10 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "AP_Follow_config.h"
+
+#if AP_FOLLOW_ENABLED
+
 #include <AP_HAL/AP_HAL.h>
 #include "AP_Follow.h"
 #include <ctype.h>
@@ -534,3 +538,5 @@ AP_Follow &follow()
 }
 
 }
+
+#endif

libraries/AP_Follow/AP_Follow.h

@@ -13,6 +13,9 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #pragma once
+#include "AP_Follow_config.h"
+
+#if AP_FOLLOW_ENABLED
 
 #include <AP_Common/AP_Common.h>
 #include <AP_Common/Location.h>
@@ -160,3 +163,5 @@ private:
 namespace AP {
     AP_Follow &follow();
 };
+
+#endif

libraries/AP_Follow/AP_Follow_config.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#ifndef AP_FOLLOW_ENABLED
+#define AP_FOLLOW_ENABLED 1
+#endif