+Kernel:
+ - optimize an internal data structure (replace boost::circular_buffer_space_optimized by
+ std::deque to store pending and unmatched Comms in Mailboxes). It is actually a revert
+ to what was used a few years back. The boost structure had a lower memory footprint than
+ deques, but it appeared that their "space_optimized" character was generating a huge lot
+ of refcount changes on the stored Comms.
+