Issue #177: TCP+SNI proxy does not work with PROXY protocol

The TCP+SNI proxy fails when used behind a router which uses
the HAProxy PROXY protocol since it will not properly
decode the ClientHello message from the TLS handshake.

Adding the proxyproto listener support to the TCP listener
removes fixes this.

listen.go

@@ -52,6 +52,7 @@ func listenAndServeTCP(l config.Listen, h proxy.TCPProxy) {
 	if err != nil {
 		exit.Fatal("[FATAL] ", err)
 	}
+	ln = &proxyproto.Listener{Listener: tcpKeepAliveListener{ln.(*net.TCPListener)}}
 	defer ln.Close()
 
 	// close the socket on exit to terminate the accept loop