Current options to set the locale are convoluted:
- An explicit locale *must* be given, while a sane default would be
to use the user environment.
- Then there are two options that were useful while testing locale
handling: read environment variables or use `setlocale`. But the
program has already called:
```
setlocale(LC_ALL, "");
```
so it turns out the two options lead to the same results.
Remove options `--locale-from-env` and `--locale-from-setlocale`
and make the locale default to the user environment.
Pierre Le Marre