You need the following files froma a Mediawiki installation in this directory:

includes/CoreParserFunctions.php
includes/Defines.php
includes/Hooks.php
includes/ImageGallery.php
includes/MagicWord.php
includes/MessageCache.php
includes/Namespace.php
includes/ObjectCache.php
includes/ParserOptions.php
includes/ParserOutput.php
includes/Parser.php
includes/Sanitizer.php
includes/SpecialPage.php
includes/StringUtils.php
includes/XmlFunctions.php
includes/Xml.php

includes/normal/UtfNormalData.inc
includes/normal/UtfNormalDataK.inc
includes/normal/UtfNormal.inc
includes/normal/UtfNormalUtil.inc

languages/Language.php
languages/Names.php

languages/messages/MessagesEn.php


The easiest is to take the "includes" and "languages" folder from a normal Mediawiki
installation and copy them into this directory.

The last tested Mediawiki version is 1.11.1. You can get it from
http://www.mediawiki.org/wiki/Download
