PATCH: Add x86_64/bits/resource.h

[Roland McGrath]

I think it warrants a comment that the purpose of all the unions is to have
the kernel-compatible layout while keeping the API type as 'long int', and
among machines where __syscall_slong_t is not 'long int' this only does the
right thing for little-endian ones (but the only such case qualifies).

It would be good to let all the machine maintainers verify that 
((__rlim_t) -1) is really the same as ((unsigned long int)(~0UL)).
I looked at all the headers and I'm pretty sure it's true, but
I could have missed something.

I think we may also still be waiting for anyone to object to the notion of
using anonymous __extension__ union in public header files.


Thanks,
Roland