This introduces a pull stat type in addition to the push stat type.
A pull stat takes a method on construction which knows how to update the stat on request.
In this way, special interfaces for pull stat collection are not necessary.
Even when an avatar is standing still, it's sending in a constant stream of AgentUpdate packets that the client creates new UDPPacketBuffer objects to handle.
This option pools those objects. This reduces memory churn.
Currently off by default. Works but the scope can be expanded.
This is controlled via the "debug lludp start <in|out|all>" and "debug lludp stop <in|out|all>" region console commands.
The command "debug lludp status" will show current status.
