AP_Common: Add a radian method for getting location bearings

libraries/AP_Common/Location.h

@@ -86,6 +86,8 @@ public:
 
     // return bearing in centi-degrees from location to loc2
     int32_t get_bearing_to(const struct Location &loc2) const;
+    // return the bearing in radians
+    float get_bearing(const struct Location &loc2) const { return radians(get_bearing_to(loc2) * 0.01f); } ;
 
     // check if lat and lng match. Ignore altitude and options
     bool same_latlon_as(const Location &loc2) const;