Buffer: use pool allocator, 20% gain in perf_transport.

Change-Id: Ie551c30be326b773f89f8d4eb141e74de362be7a
Reviewed-on: http://gerrit.aldebaran.lan:8080/9900
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: cgestes <gestes@aldebaran-robotics.com>