Allow forum topicrow pagination to use topicrow values

In viewforum.php on like 976, pagination currently does not use the topic_row values that the event core.viewforum_modify_topicrow allows you to change.  I need either add $replies to the above event, or more simply I can change $replies within the pagination to $topic_row['REPLIES'] to produce the same affect.  This pull request changes two variables within pagination on like 976 to use the values from topic_row, so they can be edited and reflected by event modification.