* Write magic number and system information into the file.
* Layout is <magic> <network> [<len> <byteorder> <sizeof int> <sizeof long>
* <sizeof ptr>] where <len> is the length of the byteorder hexa string.
* Write magic number and system information into the file.
* Layout is <magic> <network> [<len> <byteorder> <sizeof int> <sizeof long>
* <sizeof ptr>] where <len> is the length of the byteorder hexa string.