Try to give a hint when an argument doesn't match

```
$./tail_ex.native -help
tail: unknown option `-h'. Did you mean `--help' ?
Usage: tail [OPTION]... [FILE]...
Try `tail --help' for more information.
```
```
$./tail_ex.native --n10
tail: unknown option `--n10'. Did you mean `-n' ?
Usage: tail [OPTION]... [FILE]...
Try `tail --help' for more information.
```
It's better to replace `?hint` by `?hints` which is a list and do the rendering here, rather than repeating it in the various `Not_found` case. This will also make quoting correct.