PATCH: Use unsigned long int in __bswap_64 for __WORDSIZE == 64

[Roland McGrath]

> I don't think it is worth the complexity since there is a check
> for __WORDSIZE already.

I consider it less complexity than repeating a function definition.
It also will make for a simple and obvious change if we later conclude
that just using uint64_t directly is an OK thing to do.


Thanks,
Roland