AP_Math: Vector2f::projected made const

libraries/AP_Math/vector2.cpp

@@ -295,7 +295,7 @@ void Vector2<T>::project(const Vector2<T> &v)
 
 // returns this vector projected onto v
 template <typename T>
-Vector2<T> Vector2<T>::projected(const Vector2<T> &v)
+Vector2<T> Vector2<T>::projected(const Vector2<T> &v) const
 {
     return v * (*this * v)/(v*v);
 }

libraries/AP_Math/vector2.h

@@ -161,7 +161,7 @@ struct Vector2
     void project(const Vector2<T> &v);
 
     // returns this vector projected onto v
-    Vector2<T> projected(const Vector2<T> &v);
+    Vector2<T> projected(const Vector2<T> &v) const;
 
     // adjust position by a given bearing (in degrees) and distance
     void offset_bearing(T bearing, T distance);