new-raknet branch support

[bennytheg]

When I attempt to use GAC with the new-raknet branch of nukkit, I get this error: https://pastebin.com/aqLb7Pk9

Apparently GAC doesn't support new-raknet, which is sad because I believe this is the only anti-cheat software on nukkit.. And with my server becoming more and more popular, more and more hackers begin to arrive and ruin everyone's fun. It would be great if you could support GAC to work with new-raknet builds!