[MAJOR] replaced rbtree with ul2tree.

The rbtree-based wait queue consumes a lot of CPU. Use the ul2tree
instead. Lots of cleanups and code reorganizations made it possible
to reduce the task struct and simplify the code a bit.
diff --git a/src/haproxy.c b/src/haproxy.c
index f8946f9..5776d18 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -269,6 +269,7 @@
 
 void dump(int sig)
 {
+#if 0
 	struct task *t;
 	struct session *s;
 	struct rb_node *node;
@@ -290,6 +291,7 @@
 			 s->req->l, s->rep?s->rep->l:0, s->cli_fd
 			 );
 	}
+#endif
 }
 
 #ifdef DEBUG_MEMORY