* grub-core/net/http.c (parse_line): Handle response 206.
	(http_receive): Stall if too many packets are in the queue.
	(http_establish): Fix range header.
	(http_seek): Fix double free.
	(http_close): Likewise.
	(http_packets_pulled): New function.
	(grub_http_protocol): Set http_seek
	* grub-core/net/tcp.c (grub_net_tcp_socket): New field `i_stall'.
	(ack_real): Set window depending on i_stall.
	(grub_net_send_tcp_packet): Likewise.
	(grub_net_tcp_stall): New function.
	(grub_net_tcp_unstall): Likewise.
	* include/grub/net/tcp.h (grub_net_tcp_stall): New proto.
	(grub_net_tcp_unstall): Likewise.