* add ipv6 to xnet.StackAsync
* dns improvements
* improve DNS workings of StackAsync
* add tentative ICMPv6
* work on prefixes and fix some small bugs, plan UDP/TCP6
* fix bugs in StackAsync and ipv4.Prefix.Contains
* update arpsubtable
* completely remove legacy internet.StackIP for StackIPv4/v6
* ipv4/ipv6 tcp/udp
* add TCP6/UDP6 dialing APIs
* add xnet.Stack6 interface
* more ipv6 integration into StackAsync; various tweaks to lneto and documentation+TODOs
* add stack6 tests
* replace netip.Prefix with ipv4.Prefix where it makes sense
* begin adding icmp client
* rely on anon structs
* add tests
* tests passing
* icmp fleshed out
* rework icmp to include ip addr
* rename StackAsync.Demux/Encapsulate to RecvEthernet and SendEthernet
* remove legacy unreachable TCP tests
* remove uses of deprecated internet.StackNode in preference of lneto.StackNode
* documentation
* rename methods to signal no I/O happening
* pcap: reuse Frame memory
* slog: reduce heap allocations of addresses; also prevent heap alloc of dhcp options in pcap
* dns: heapless improvement; add StackAsync buffer for more heapless operation; start thinking of errors
* errors: begin standardise errors in lneto
* errors: finish standardization of errors
* fix merge issues
* add more lneto errors to rest of package
* format errors.go
* tcp: mss honoring; accept syn with ECE/CWR flags; add RSTQueue type
* tcp: move option logic to own file
* remove prints in pcap
* add MSS send threshold inspired by linux/freebsd/lwip thresh
Pat Whittingslow