Make NetworkEventFiringHandler sharable

Fixes #356

src/main/java/cpw/mods/fml/common/network/NetworkEventFiringHandler.java

@@ -3,6 +3,7 @@ package cpw.mods.fml.common.network;
 import org.apache.logging.log4j.Level;
 import cpw.mods.fml.common.FMLLog;
 import cpw.mods.fml.common.network.internal.FMLProxyPacket;
+import io.netty.channel.ChannelHandler.Sharable;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.SimpleChannelInboundHandler;
 
@@ -14,6 +15,7 @@ import io.netty.channel.SimpleChannelInboundHandler;
  * @author cpw
  *
  */
+@Sharable
 public class NetworkEventFiringHandler extends SimpleChannelInboundHandler<FMLProxyPacket> {
     private FMLEventChannel eventChannel;