- add /etc/subuid and /etc/subgid files (FS#68741)

- use systemd recommended settings for /etc/nsswitch.conf

- implement FS#72870

- make append_path function available to profile.d scripts (see FS#66338)

This will prevent root login with an empty password on a fresh Arch Linux
installation.

This is only about the default behaviour, you could restore the previous one by
running `passwd -d root'.
Please note, this is not recommended and behave inconsistenly between
applications.

We use a trick in the shadow file to set a default password which never allow
login by using this password.

The special value '*' is used in the shadow file.
We don't use '!', '!!', '!*' on purpose.
The special '!' char, which should mean password locked (and not account locked)
is interpreted by some applications (e.g. sshd) as an account locked and will
prevent root login.

This change was suggested by Lennart Poettering and Zbigniew Jedrzejewski-Szmek
to security@archlinux.org.

- fix FS#66499

- Restore ID
- Add BUILD_ID
- Add DOCUMENTATION_URL

- fid FS#58499

$ locale | cut -d= -f1 | grep -v LC_ALL | sed /^LANG$/aLANGUAGE | paste -sd' ' | fold -w 70 -s | sed -e 's/ $/ \\/' -e '1s/^/export /' -e '2,$s/^/       /'

- Restore previous loading of /etc/locale.sh

- fix FS#56688

- empty passwd,gpasswd,group,gpasswd (need systemd >v235)

- package version bump to 4

pwck/grpck don't support comments in these files.
Thanks to grawity for reporting it.

- use uid/gid in PKGBUILD to avoid dependency to itself
- add nobody as a static user (FS#55589)
- add headers to passwd,shadow,group,gshadow
- sort deps and backup alphabetically

Glibc depends on filesystem, so it creates a depency loop.

- define archlinux default PATH with a systemd environment generator