#499 Improve BZFSNetLogCB efficiency by caching memory allocation

[Russell Bryant]

This patch improves the efficiency of the BZFSNetLogCB class.

Specifically, the network log callback was doing a malloc() and free() every time it needed to send out a network event through the worldEventManager. Instead of continuously calling malloc()/free(), this patch caches the allocation for reuse and increases its size as necessary.

[Russell Bryant]