Help improve the internationalisation of MediaWiki. The corresponding bug report is https://bugzilla.wikimedia.org/show_bug.cgi?id=68750 . Detailed steps:

1. Keep https://www.mediawiki.org/wiki/Localisation#Internationalization_hints in mind, study the messages API manual at https://www.mediawiki.org/wiki/Manual:Messages_API for PHP until you fully understand the conversion table: https://www.mediawiki.org/wiki/Manual:Messages_API#Help_with_replacing_deprecated_wfMsg.2A_functions .
2. Pick 1 extensions/* directory from those mentioned at https://bugzilla.wikimedia.org/show_bug.cgi?id=68750#c0 . Ensure it's not already being worked on at https://gerrit.wikimedia.org/r/#/q/message:wfMsg+project:%255Emediawiki/extensions/.%252B+is:open,n,z .
3. Update the code which uses wfMsg* functions, as explained in the manual linked above; test and submit your patch to gerrit as explained in the general suggested reading material at https://www.mediawiki.org/wiki/Google_Code-in_2014#Suggested_reading .
   Remember to mention wfMsg* and bug 68750 in the commit message as explained in https://www.mediawiki.org/wiki/Gerrit/Commit_message_guidelines : that will be enough for the mentors to know of your work; this task will be accepted here when one patch is merged.

Students are required to read Wikimedia's general instructions at https://www.mediawiki.org/wiki/Google_Code-in_2014#Instructions_for_GCI_students first.