Copter: enable use of AHRS_NavEKF

ArduCopter/ArduCopter.pde

@@ -316,7 +316,12 @@ AP_GPS_None     g_gps_driver;
   #error Unrecognised GPS_PROTOCOL setting.
  #endif // GPS PROTOCOL
 
-static AP_AHRS_DCM ahrs(ins, g_gps);
+// Inertial Navigation EKF
+#if AP_AHRS_NAVEKF_AVAILABLE
+AP_AHRS_NavEKF ahrs(ins, barometer, g_gps);
+#else
+AP_AHRS_DCM ahrs(ins, barometer, g_gps);
+#endif
 
 #elif HIL_MODE != HIL_MODE_DISABLED
 // sensor emulators