Store a bitmap of active hooks on the client side to try to avoid
server calls for hooks that are not set.

diff --git a/server/queue.c b/server/queue.c
index a0617a1..bdce76a 100644
--- a/server/queue.c
+++ b/server/queue.c
@@ -1572,6 +1572,8 @@
     struct msg_queue *queue = get_current_queue();
     user_handle_t get_win = get_user_full_handle( req->get_win );
 
+    reply->active_hooks = get_active_hooks();
+
     if (!queue) return;
     gettimeofday( &queue->last_get_msg, NULL );