AP_AHRS: move location_update to Location and rename to offset_bearing

libraries/AP_AHRS/AP_AHRS.h

@@ -30,6 +30,7 @@
 #include <AP_Baro/AP_Baro.h>
 #include <AP_Param/AP_Param.h>
 #include <AP_Common/Semaphore.h>
+#include <AP_Common/Location.h>
 
 class OpticalFlow;
 #define AP_AHRS_TRIM_LIMIT 10.0f        // maximum trim angle in degrees

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -989,7 +989,7 @@ bool AP_AHRS_DCM::get_position(struct Location &loc) const
     if (_flags.fly_forward && _have_position) {
         float gps_delay_sec = 0;
         _gps.get_lag(gps_delay_sec);
-        location_update(loc, _gps.ground_course_cd() * 0.01f, _gps.ground_speed() * gps_delay_sec);
+        loc.offset_bearing(_gps.ground_course_cd() * 0.01f, _gps.ground_speed() * gps_delay_sec);
     }
     return _have_position;
 }