2012/3/1 Paul Eggert <eggert@cs.ucla.edu>
> -    unsigned long int magic; /* Magic number to check header integrity.  */
> +    uint64_t magic;  /* Magic number to check header integrity.  */

Not needed for Windows 64, since the magic number fits in 32 bits.

If it fits in 32 bits, then it shouldn't be long in first place? 
Unsigned int is enough and will be 32 bits wide ofr x86 and x64.

--
Fabrice