ArduCopter: made Robert's new yaw method optional (off by default).

Add this line to APM_Config.h to enable Robert's yaw
#define ALTERNATIVE_YAW_MODE ENABLED

ArduCopter/Attitude.pde

@@ -409,9 +409,23 @@ get_nav_yaw_offset(int yaw_input, int reset)
 		return ahrs.yaw_sensor;
 
 	}else{
+#if ALTERNATIVE_YAW_MODE == ENABLED
 		_yaw = nav_yaw + (yaw_input / 50);
 		return wrap_360(_yaw);
+#else
+		// re-define nav_yaw if we have stick input
+		if(yaw_input != 0){
+			// set nav_yaw + or - the current location
+			_yaw = yaw_input + ahrs.yaw_sensor;
+			// we need to wrap our value so we can be 0 to 360 (*100)
+			return wrap_360(_yaw);
+
+		}else{
+			// no stick input, lets not change nav_yaw
+			return nav_yaw;
 		}
+#endif
+	}
 }
 
 static int16_t get_angle_boost(int16_t value)

ArduCopter/config.h

@@ -989,4 +989,8 @@
 # define RETRO_LOITER_MODE DISABLED
 #endif
 
+#ifndef ALTERNATIVE_YAW_MODE
+# define ALTERNATIVE_YAW_MODE DISABLED
+#endif
+
 #endif // __ARDUCOPTER_CONFIG_H__