[ticket/15735] Add posting_topic_review_row_content_after template event

Needed for extensions who adds information at the end of the message
(such as moderator messages).

PHPBB3-15735

phpBB/styles/prosilver/template/posting_topic_review.html

@@ -60,6 +60,8 @@
 
 			<div class="content">{topic_review_row.MESSAGE}</div>
 
+			<!-- EVENT posting_topic_review_row_content_after -->
+
 			<!-- IF topic_review_row.S_HAS_ATTACHMENTS -->
 				<dl class="attachbox">
 					<dt>{L_ATTACHMENTS}</dt>