[PATCH] io: Use gnulib fts implementation (BZ 22944, BZ 20331)

[Bruno Haible]

Adhemerval Zanella wrote:
>  create mode 100644 io/cycle-check.c
>  create mode 100644 io/cycle-check.h
>  create mode 100644 io/dev-ino.h
>  create mode 100644 io/fts-cycle.c
>  create mode 100644 io/hash.c
>  create mode 100644 io/hash.h
>  create mode 100644 io/i-ring.c
>  create mode 100644 io/next-prime.c
>  create mode 100644 io/next-prime.h
>  create mode 100644 io/same-inode.h

That's 10 new files, in a directory that already has 104 C source code files
(excluding tests), and which exist only for use by the fts.c, fts64.c,
fts64-time64.c compilation units.

For maintainability, I would suggest to put all these 10 files, and possibly
also fts.c and fts.h, into a subdirectory of io/.

Like the directory resolv/nss_dns/ under resolv/.
Or like the directories nss/nss_compat/, nss/nss_db/, nss/nss_files/
under nss/.

Bruno