* Moved SpecialInterwiki class to SpecialInterwiki_body.php, load it only when needed
* Use $wgSpecialPages to register the page, doesn't need to create an instance at each run of the wiki
* Rewritten urls, use action parameter instead of do
* Added action=edit, allow to modifiy a prefix without needing to delete and recreate it
* Killed hooks to register the new log, use directly $wgLog* variables
* Modified log recording system: don't hardcode action text, instead use message so that they can be translated depending of user language like other log messages, i used iw_ as prefix for actions, otherwise there'll a "undelete" link near deleted items, kept default message for backward compatibility
* Also applied a patch by SPQRobin: added some ids and classes to the html source and modify page header when the user isn't allowed to modify interwiki prefixes
