Possible readdir() problem on LFS (beta4)

[Andrej Borsenkow]

>
> Ok - I'll do the same wrapping for readdir64 and telldir64
> as I do for the other calls.
>
>

Jeremy, RealintUNIX (at least, the verion I have) needs <unistd.h> for _any_
LFS stuff before most other headers. Current check for dirent64 will fail
without it.

I wonder, may be simply add #inlcude <unistd.h> to confdefs.h if we are on
Reliant? This is ugly, but at least, all future tests (if any) are sage.

/andrej