Switch from calloc() to malloc()+memset() to match the practices used

almost everywhere else.

src/net/netdevice.c

  */
 struct net_device * alloc_netdev ( size_t priv_size ) {
 	struct net_device *netdev;
+	size_t total_len;
 
-	netdev = calloc ( 1, sizeof ( *netdev ) + priv_size );
+	total_len = ( sizeof ( *netdev ) + priv_size );
+	netdev = malloc ( total_len );
 	if ( netdev ) {
+		memset ( netdev, 0, total_len );
 		INIT_LIST_HEAD ( &netdev->references );
 		INIT_LIST_HEAD ( &netdev->tx_queue );
 		INIT_LIST_HEAD ( &netdev->rx_queue );

src/net/tcp.c

 static struct tcp_connection * alloc_tcp ( void ) {
 	struct tcp_connection *conn;
 
-	conn = calloc ( 1, sizeof ( *conn ) );
+	conn = malloc ( sizeof ( *conn ) );
 	if ( conn ) {
 		DBGC ( conn, "TCP %p allocated\n", conn );
+		memset ( conn, 0, sizeof ( *conn ) );
 		conn->tcp_state = conn->prev_tcp_state = TCP_CLOSED;
 		conn->snd_seq = random();
 		conn->timer.expired = tcp_expired;