[locale] prefer native language and country names when available

This basically means we talk about localization in the respective
localized variant. e.g. "German (Germany)" ➡ "Deutsch (Deutschland)".

If geoip lookup failed or isn't configured for whatever reason it's a
stretch to expect the user to know english enough to find their own
language. Preferring the localized strings resolves this issue.

Additionally this happens to bypass #712 respectively
https://bugreports.qt.io/browse/QTBUG-34287
as the native names are properly spelled. So, as long as Qt has localized
names the names will also be properly spelled.

src/modules/keyboard/KeyboardPage.cpp

@@ -369,6 +369,8 @@ KeyboardPage::onActivate()
     {
         const auto langParts = lang.split( '_', QString::SkipEmptyParts );
 
+        // Note that this his string is not fit for display purposes!
+        // It doesn't come from QLocale::nativeCountryName.
         QString country = QLocale::countryToString( QLocale( lang ).country() );
         cDebug() << " .. extracted country" << country << "::" << langParts;
 

src/modules/locale/LocalePage.cpp

@@ -477,8 +477,13 @@ LocalePage::prettyLCLocale( const QString& lcLocale ) const
 
     QLocale locale( localeString );
     //: Language (Country)
-    return tr( "%1 (%2)" ).arg( QLocale::languageToString( locale.language() ) )
-                          .arg( QLocale::countryToString( locale.country() ) );
+    const QString lang = !locale.nativeLanguageName().isEmpty() ?
+                         locale.nativeLanguageName() :
+                         QLocale::languageToString( locale.language() );
+    const QString country = !locale.nativeCountryName().isEmpty() ?
+                            locale.nativeCountryName() :
+                            QLocale::countryToString( locale.country() );
+    return tr( "%1 (%2)" ).arg( lang ).arg( country );
 }
 
 void

src/modules/welcome/WelcomePage.cpp

@@ -345,4 +345,3 @@ WelcomePage::focusInEvent( QFocusEvent* e )
         ui->languageWidget->setFocus();
     e->accept();
 }
-