socket: add support for TCP fast Open

TCP Fast Open (TFO) speeds up the opening of successiveTCP)
connections between two endpoints.It works by using a TFO cookie
in the initial SYN packet to authenticate a previously connected
client. It starts sending data to the client before the receipt
of the final ACK packet of the three way handshake is received,
skipping a round trip and lowering the latency in the start of
transmission of data.