[Form][RFC] added failing test for 'en_GB' locale

I was having some trouble with the list of locales available via the `LocaleType`.  When the default locale is `en_US` or `en_CA` it works as expected, but for `en_GB` the list has just one entry:

```php
array('tzm' => 'Central Morocco Tamazight')
```

Further, for `fr`, the list is correct, but for `fr_CA` it is not:

```php
array(
    'si' => 'singhalais',
    'to' => 'tongan'
)
```

I have wrote a simple failing test based on this issue.