AP_ExternalControl: add REP-147 Global Position Control

Signed-off-by: Ryan Friedman <ryanfriedman5410+github@gmail.com>

ArduPlane/AP_ExternalControl_Plane.cpp

@@ -0,0 +1,22 @@
+/*
+  external control library for plane
+ */
+
+
+#include "AP_ExternalControl_Plane.h"
+#if AP_EXTERNAL_CONTROL_ENABLED
+
+#include "Plane.h"
+
+/*
+  Sets the target global position for a loiter point.
+*/
+bool AP_ExternalControl_Plane::set_global_position(const Location& loc)
+{
+
+    // set_target_location already checks if plane is ready for external control.
+    // It doesn't check if flying or armed, just that it's in guided mode.
+    return plane.set_target_location(loc);
+}
+
+#endif // AP_EXTERNAL_CONTROL_ENABLED

libraries/AP_ExternalControl/AP_ExternalControl.h

@@ -8,6 +8,7 @@
 
 #if AP_EXTERNAL_CONTROL_ENABLED
 
+#include <AP_Common/Location.h>
 #include <AP_Math/AP_Math.h>
 
 class AP_ExternalControl
@@ -24,9 +25,18 @@ public:
         return false;
     }
 
+    /*
+        Sets the target global position with standard guided mode behavior.
+    */
+    virtual bool set_global_position(const Location& loc) WARN_IF_UNUSED {
+        return false;
+    }
+
     static AP_ExternalControl *get_singleton(void) WARN_IF_UNUSED {
         return singleton;
     }
+protected:
+    ~AP_ExternalControl() {}
 
 private:
     static AP_ExternalControl *singleton;