added dummy save() method to AP_IMU_Shim

git-svn-id: https://arducopter.googlecode.com/svn/trunk@1781 f9c3cf11-9bcb-44bc-f272-b75c42450872

libraries/AP_IMU/AP_IMU_Shim.h

@@ -48,6 +48,9 @@ public:
 	///
 	void		set_accel(Vector3f v) { _accel = v; _updated = true; }
 
+	// dummy save method
+	void		save(void) { }
+
 private:
 	/// set true when new data is delivered
 	bool		_updated;