plugin hook for update_unseen

doc/hook/update_unseen.bb

@@ -0,0 +1,9 @@
+[h3]update_unseen[/h3]
+
+Called prior to automatically marking items 'seen'; allowing a plugin the choice to not perform this action.
+
+hook data
+
+[ 'channel_id' => local_channel(), 'update' => 'unset' ];
+
+If 'update' is set to 0 or false on return, the update operation is not performed.