net/gamenetworkingsockets: add new ports.

GameNetworkingSockets is Valve's semi-recently open-sourced networking
library.

It supports a number of very useful features, including:

• Reliable & unreliable messages over UDP.
• Robust message fragmentation & reassembly.
• P2P networking / NAT traversal. Encryption.

PR: 256295
Reported by: Karsten Pedersen <kpedersen at disroot.org>