Merge branch 'fjl-p2p-handshake-2' into poc-9

eth/backend.go

eth/protocol.go

p2p/discover/node.go

p2p/discover/node_test.go

p2p/handshake.go

p2p/handshake_test.go

p2p/message.go

p2p/message_test.go

p2p/peer.go

p2p/peer_test.go

p2p/rlpx.go

p2p/rlpx_test.go

p2p/server.go

p2p/server_test.go

whisper/peer.go