Fix locale issue on unix systems

QSystemLocale::query() was missing the LanguageId QueryType. Therefore
QSystemLocale::fallbackLocale() was always used as default language,
which reads environment variables in the order: LC_ALL -> LC_NUMERIC ->
LANG. The correct behaviour is to read LC_ALL -> LC_MESSAGES -> LANG.
This leads to problems for users that want to use english language, but
non-english localization features (date, number formats etc.)

Change-Id: I4310537dac8622a3dd79231fbad58e22f20ca262
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: John Layt <jlayt@kde.org>

src/corelib/tools/qlocale_unix.cpp

@@ -244,6 +244,8 @@ QVariant QSystemLocale::query(QueryType type, QVariant in) const
         return lc_messages.createSeparatedList(in.value<QStringList>());
     case LocaleChanged:
         Q_ASSERT(false);
+    case LanguageId:
+        return lc_messages.language();
     default:
         break;
     }