Add LocklessQueue::Pinner class

This will allow reading messages from queues without copying, which is
helpful for speeding up the processing of images.

Change-Id: Ia4bb98afa6fe1c1b5cc186e3071c7458f143d77d
diff --git a/aos/ipc_lib/lockless_queue_test.cc b/aos/ipc_lib/lockless_queue_test.cc
index 65b2a15..4e84b9f 100644
--- a/aos/ipc_lib/lockless_queue_test.cc
+++ b/aos/ipc_lib/lockless_queue_test.cc
@@ -44,6 +44,7 @@
   LocklessQueueTest() {
     config_.num_watchers = 10;
     config_.num_senders = 100;
+    config_.num_pinners = 5;
     config_.queue_size = 10000;
     // Exercise the alignment code.  This would throw off alignment.
     config_.message_data_size = 101;