* chown: support '.' as 'user.group' separator (like ':')
It also manages the case:
user.name:group (valid too)
Should fix:
gnu/tests/chown/separator.sh
`LANGUAGE=C` is not enough, `LC_ALL=C` is needed as the environment
variable that overrides all the other localization settings.
e.g.
```bash
$ LANGUAGE=C id foobar
id: ‘foobar’: no such user
$ LC_ALL=C id foobar
id: 'foobar': no such user
```
* replace `LANGUAGE` with `LC_ALL` as environment variable in the tests
* fix the the date string of affected uutils
* replace `‘` and `’` with `'`