[MEDIUM] indicate a reason for a task wakeup

It's very frequent to require some information about the
reason why a task is running. Some flags have been added
so that a task now knows if it got woken up due to I/O
completion, timeout, etc...
diff --git a/src/proto_uxst.c b/src/proto_uxst.c
index 2185f9f..4eab55e 100644
--- a/src/proto_uxst.c
+++ b/src/proto_uxst.c
@@ -520,7 +520,7 @@
 			t->expire = s->req->rex;
 		}
 
-		task_wakeup(t);
+		task_wakeup(t, TASK_WOKEN_INIT);
 
 		l->nbconn++; /* warning! right now, it's up to the handler to decrease this */
 		if (l->nbconn >= l->maxconn) {