hm, either that test doesn't work...
or this one:
#define _GNU_SOURCE
#include "sysdep.h"
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
is pulling some other stuff in...
as mentioned before, there realy has to be some other header with a define, which then in term gets pulled in before.