Rover: use get_projected_position()

this will make for more accurate turns in missions

APMrover2/APMrover2.pde

@@ -807,7 +807,7 @@ static void update_GPS(void)
         }
     }
 
-    have_position = ahrs.get_position(&current_loc);
+    have_position = ahrs.get_projected_position(&current_loc);
 
 	if (g_gps->new_data && g_gps->status() >= GPS::GPS_OK_FIX_3D) {
 		gps_fix_count++;