The property "catslug" missing on view category.

This patch adds a property "catslug" to the objects of the articles on view "Category". This is a patch for Joomla! 2.5. 
This issue does not exist in Joomla! 3.

Joomla!Code Tracker Page:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33665