Validate whether the language from API is known while trying to display

See https://bugzilla.wikimedia.org/show_bug.cgi?id=54725

Change-Id: Ie77f7cd02d37338a6b65db653c2ba3b35906dac0
Merge branch 'master' of github.com:wikimedia/jquery.uls
Localisation updates from http://translatewiki.net.
Fix typo