Cleanup r26692:

Cleanup r26692:
* Use content language, not UI language, when adding language suffix to OpenSearch description
* Use $wgContLang->getLanguageName() instead of grabbing a whole array of every name ever :)
* If there isn't a defined language name for this code, don't spew a PHP notice and output "()". Use the language code instead, so non-standard and as-yet-unused languages won't break.