Missing commands

List of commands not in this repo but present in NetBSD src:

```
at
base64
bc
cap_mkdb
chroot
cu
dev_mkdb
diff
diff3
factor
ftp
gzip
lndir
newsyslog
nologin
pathchk
progress
qsubst
rdate
realpath
tftp
spell
su
truncate
users
vacation
which
who
```

Also `test`, `checknr` should be updated.