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>