Second MR with our work on the IPv6 stack for #SerenityOS just landed!

This means that on the master branch, you can already IPv6 ping a SerenityOS host, and it will handle a neighbor solicitation (equivalent to ARP) and actual ICMPv6 Echo Request packets :blobcat3c:

Next up: refactoring IPv4 sockets to make them generic by @filmroellchen, and then we can add some more glue code for handling TCP/UDP. Really really excited for this :ablobcatbongo: