[MAJOR] replace ultree with ebtree in wait-queues

The ultree code has been removed in favor of a simpler and
cleaner ebtree implementation. The eternity queue does not
need to exist anymore, and the pool_tree64 has been removed.

The ebtree node is stored in the task itself. The qlist list
header is still used by the run-queue, but will be able to
disappear once the run-queue uses ebtree too.
diff --git a/src/appsession.c b/src/appsession.c
index e1a01cc..fcd4e02 100644
--- a/src/appsession.c
+++ b/src/appsession.c
@@ -91,9 +91,7 @@
 		if ((appsess_refresh = pool_alloc2(pool2_task)) == NULL)
 			return -1;
 
-		appsess_refresh->wq = NULL;
-		appsess_refresh->qlist.p = NULL;
-		appsess_refresh->state = TASK_IDLE;
+		task_init(appsess_refresh);
 		appsess_refresh->context = NULL;
 		tv_ms_add(&appsess_refresh->expire, &now, TBLCHKINT);
 		appsess_refresh->process = appsession_refresh;