This complements patch a148c7b5d71d244, where languageToCode(),
countryToCode() scriptToCode() methods were introduced, with matching
codeToLanguage(), codeToCountry(), and codeToScript() methods.
This allows us to remove the use of private Qt Core API in Qt Linguist.
[ChangeLog][QtCore][QLocale] Added static codeToLanguage(),
codeToCountry(), codeToScript() methods that convert ISO code strings
to the respective enum values.
Change-Id: If5c0843a718c006ade086a6f74ceb86ac6e0fce4
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
e7c028bb9c