Also global_is_set to is_set.

issue #6024

Merge branch '5885-add-the-language-afrikaans-south-africa-af_za-chinese-taiwan-zh_tw' into '1.4-dev'

Resolve "Add the language Afrikaans (South Africa) (af_ZA) Chinese (Taiwan) (zh_TW)"

Closes #5885

See merge request fusiondirectory/fd!390

(cherry picked from commit 595a6269)

de11ec69  feat(locales) Add the language Afrikaans (South Africa) (af_ZA) Chinese (Taiwan) (zh_TW)

Renamed all languages to include a country as well, to match debian
 locale names.
Also added a fallback on the 2-letter locale in all cases. (falling back
 still triggers a PHP error)

issue #5819

issue #5820

issue #5820

When no language at all was asked by the browser and language was set to
 automatic FD would select Arabic because of sorting. Now it will
 default to English

issue #5820

This also fix the workflow to make sure the language in the header is
 correct in all cases.
A PHP error is triggered if setlocale fails or if the wrong language
 header was sent.

issue #5820