Sort language drop down by language code.

This seemed the logical place to do it, because it's essentially
a presentation thing (so in Template, not Locale). There's likely
something to be said for sorting by key aswell as sorting by
translated language name. Picked key for now, seems most predictable.

lib/SimpleSAML/XHTML/Template.php

@@ -330,6 +330,7 @@ class SimpleSAML_XHTML_Template
     private function generateLanguageBar()
     {
         $languages = $this->translator->getLanguage()->getLanguageList();
+        ksort($languages);
         $langmap = null;
         if (count($languages) > 1) {
             $parameterName = $this->getTranslator()->getLanguage()->getLanguageParameterName();