optimization: use netlink to hear interfaces changing

[rektide]

Hello. On many *nix systems one can use netlink to listen for changes to network interfaces. It would be cool to have this optimization to this great library.

Some example information on how others have achieved this:
https://stackoverflow.com/questions/27008067/how-to-get-notified-about-network-interface-changes-with-netlist-and-rtmgrp-link

[martinheidegger]

@rektide Cool! thank you for researching this. Definitely a neat optimization step. Might probably need some restructuring to take place though (and I need to refresh my C)