[DP-72] use a per-vnode shared buffer to serialize small messages

[qnikst]

[Imported from JIRA. Reported by Tim Watson [Administrator] @hyperthunk) as DP-72 on 2013-03-28 16:59:56]
As (another) optimisation, we could take advantage of recent improvements to the binary package that allow us to pre-allocate a buffer and re-use it for serializing small messages.