[MEDIUM] introduce task->nice and boot access to statistics

The run queue scheduler now considers task->nice to queue a task and
to pick a task out of the queue. This makes it possible to boost the
access to statistics (both via HTTP and UNIX socket). The UNIX socket
receives twice as much a boost as the HTTP socket because it is more
sensible.
diff --git a/src/proto_http.c b/src/proto_http.c
index 7b35ff7..308ecb0 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -5160,6 +5160,7 @@
 	t->logs.tv_request = now;
 	t->data_source = DATA_SRC_STATS;
 	t->data_state  = DATA_ST_INIT;
+	t->task->nice = -32; /* small boost for HTTP statistics */
 	produce_content(t);
 	return 1;
 }