Hello!

   It seems we have way too many copy&pasted fstatat code elsewhere which
   might not have been a problem until now, but with all the changes
   with "stat light" now and who knows what other additions in there in
   the future, it really helps if we have only one copy of the code.

   Hence this patch adds fstatat_common() that fills struct kstat with
   proper values and does all the AT flags parsing that's needed and
   then calls all the proper underlying functions, what's left to the
   caller now is to only copy filled out kstat buffer to the final
   destination.

Bye,
    Oleg