Re: d_off field in struct dirent and 32-on-64 emulation

* Adhemerval Zanella:

Also for glibc standpoint, although reverting it back to use getdents 
syscall for non-LFS mode might fix this issue for architectures that
provides non-LFS getdents syscall it won't be a fix for architectures 
that still provides off_t different than off64_t *and* only provides 
getdents64 syscall.

Currently we only have nios2 and csky (unfortunately).  But since generic 
definition for off_t and off64_t still assumes non-LFS support, all new
32-bits ports potentially might carry the issue.

For csky, we could still change the type of the non-standard d_off
field to long long int.  This way, only telldir would have to fail
when truncation is necessary, as mentioned below:

quoted

There is another annoying aspect: The standards expose d_off through
the telldir function, and that returns long int on all architectures
(not off_t, so unchanged by _FILE_OFFSET_BITS).  That's mostly a
userspace issue and thus needing different steps to resolve (possibly
standards action).