For the sake of DOS and Windows, provide a different way to get a

#include <stdio.h>

#include <openssl/bn.h>

#include <string.h>

#include <openssl/e_os2.h>

#ifndef OPENSSL_SYS_MSDOS

#include <unistd.h>

#else

#include <process.h>

typedef int pid_t;

#endif

#include <openssl/crypto.h>

#include "cryptlib.h"