NetHook: Create Linux version

[xPaw]

Would be nice to be able to nethook on Linux. Hook with LD_PRELOAD?

[psychonic]

#1082 could be revived

[yaakov-h]

It is quite tempting.

I'd also like it on macOS, could hook with DYLD_INSERT_BINARIES but macOS code signing and app containers might not let us (thanks, Apple Security).

[Nemirtingas]

Made it work on my ubuntu some time ago: https://github.com/Nemirtingas/SteamKit/tree/linux_hook