AllViewed allows members to mark all discussions as viewed by clicking "Mark All Viewed" 
in the main nav (path: /discussions/markallviewed)

This resets their counters for how many comments were previously in the discussion. 
Therefore, if there are 3 subsequent comments, the discussion will simply say "New",
not "3 New" because it no longer knows how many comments there were.

Normally viewing the discussion will put it back on a "X New"-style counter.

This behavior is to circumvent potential problems with massive updates to the
UserDiscussion table when "Mark All Viewed" is clicked.


**Requires Vanilla 2.0.12

To make compatible with 2.0.11 or earlier, open class.discussionmodel.php 
then go to the Get() method and find this:

   $this->AddDiscussionColumns($Data);
   
   return $Data;

and replace it with:

   $this->AddDiscussionColumns($Data);
   $this->EventArguments['Data'] = $Data;
   $this->FireEvent('AfterAddColumns');
   
   return $Data;