This is the code of my config from arduino:
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#ifndef __ARDUCOPTER_APMCONFIG_H__
#define __ARDUCOPTER_APMCONFIG_H__
// Example config file. Take a look at config.h. Any term define there can be overridden by defining it...