Spigot patch update (771): Netty: Add written bytes tracking for @bergerkiller.

https://github.com/EcoCityCraft/Spigot/commit/db79d01b57badbe014d15d0c636a1420fa853c2e

Completes update to Spigot build 771 (hidendra's pulls added in MinecraftPortCentral/MCPC-Plus@5cc4c38877d06e2487dfb8f30fff1e2ed2492ae4)