eo locale is improperly handled

#include <QCoreApplication>
#include <QLocale>
#include <QTextStream>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    auto locale = QLocale("eo");
    QTextStream(stdout)
      << locale.language() << endl            // "1"
      << locale.nativeLanguageName() << endl; // ""

    locale = QLocale(QLocale::Esperanto, QLocale::AnyCountry);
    QTextStream(stdout)
      << locale.language() << endl            // "31"
      << locale.nativeLanguageName() << endl; // "American English"

    QTextStream(stdout)
      << QLocale::Esperanto << endl                             // "32"
      << QLocale::languageToString(QLocale::Esperanto) << endl; // "Esperanto"

    return a.exec();
}