p2p: API cleanup and PoC 7 compatibility

Whoa, one more big commit. I didn't manage to untangle the
changes while working towards compatibility.

p2p/testpoc7.go

@@ -0,0 +1,40 @@
+// +build none
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"os"
+
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/obscuren/secp256k1-go"
+)
+
+func main() {
+	logger.AddLogSystem(logger.NewStdLogSystem(os.Stdout, log.LstdFlags, logger.DebugLevel))
+
+	pub, _ := secp256k1.GenerateKeyPair()
+	srv := p2p.Server{
+		MaxPeers:   10,
+		Identity:   p2p.NewSimpleClientIdentity("test", "1.0", "", string(pub)),
+		ListenAddr: ":30303",
+		NAT:        p2p.PMP(net.ParseIP("10.0.0.1")),
+	}
+	if err := srv.Start(); err != nil {
+		fmt.Println("could not start server:", err)
+		os.Exit(1)
+	}
+
+	// add seed peers
+	seed, err := net.ResolveTCPAddr("tcp", "poc-7.ethdev.com:30303")
+	if err != nil {
+		fmt.Println("couldn't resolve:", err)
+		os.Exit(1)
+	}
+	srv.SuggestPeer(seed.IP, seed.Port, nil)
+
+	select {}
+}