exp/ssh: server cleanups

server.go/channel.go:
* rename Server to ServerConfig to match Client.
* rename ServerConnection to ServeConn to match Client.
* add Listen/Listener.
* ServerConn.Handshake(), general cleanups.

client.go:
* fix bug where fmt.Error was not assigned to err

R=rsc, agl
CC=golang-dev
https://golang.org/cl/5265049

src/pkg/exp/ssh/channel.go

@@ -68,7 +68,7 @@ type channel struct {
 	weClosed    bool
 	dead        bool
 
-	serverConn            *ServerConnection
+	serverConn            *ServerConn
 	myId, theirId         uint32
 	myWindow, theirWindow uint32
 	maxPacketSize         uint32

src/pkg/exp/ssh/client.go

@@ -115,7 +115,7 @@ func (c *ClientConn) handshake() os.Error {
 		dhGroup14Once.Do(initDHGroup14)
 		H, K, err = c.kexDH(dhGroup14, hashFunc, &magics, hostKeyAlgo)
 	default:
-		fmt.Errorf("ssh: unexpected key exchange algorithm %v", kexAlgo)
+		err = fmt.Errorf("ssh: unexpected key exchange algorithm %v", kexAlgo)
 	}
 	if err != nil {
 		return err