Allow usage of RAW sockets

[G1org1owo]

The flag is already there and EthernetClass::socketBegin() already receives the socket type, but there is no way to use this without modifying the library or copying the code in socket.cpp, as all the methods working with the socket in EthernetClass are private.

I think this library should include specific IPRawClient and MacRawClient classes (and their respective servers), but in order to allow devs to expand on this without modifying the library I propose that the following socket methods be changed from private to protected.

private:
	// Opens a socket(TCP or UDP or IP_RAW mode)
	static uint8_t socketBegin(uint8_t protocol, uint16_t port);
	static uint8_t socketBeginMulticast(uint8_t protocol, IPAddress ip,uint16_t port);
	static uint8_t socketStatus(uint8_t s);
	// Close socket
	static void socketClose(uint8_t s);
	// Establish TCP connection (Active connection)
	static void socketConnect(uint8_t s, uint8_t * addr, uint16_t port);
	// disconnect the connection
	static void socketDisconnect(uint8_t s);
	// Establish TCP connection (Passive connection)
	static uint8_t socketListen(uint8_t s);
	// Send data (TCP)
	static uint16_t socketSend(uint8_t s, const uint8_t * buf, uint16_t len);
	static uint16_t socketSendAvailable(uint8_t s);
	// Receive data (TCP)
	static int socketRecv(uint8_t s, uint8_t * buf, int16_t len);
	static uint16_t socketRecvAvailable(uint8_t s);
	static uint8_t socketPeek(uint8_t s);
	// sets up a UDP datagram, the data for which will be provided by one
	// or more calls to bufferData and then finally sent with sendUDP.
	// return true if the datagram was successfully set up, or false if there was an error
	static bool socketStartUDP(uint8_t s, uint8_t* addr, uint16_t port);
	// copy up to len bytes of data from buf into a UDP datagram to be
	// sent later by sendUDP.  Allows datagrams to be built up from a series of bufferData calls.
	// return Number of bytes successfully buffered
	static uint16_t socketBufferData(uint8_t s, uint16_t offset, const uint8_t* buf, uint16_t len);
	// Send a UDP datagram built up from a sequence of startUDP followed by one or more
	// calls to bufferData.
	// return true if the datagram was successfully sent, or false if there was an error
	static bool socketSendUDP(uint8_t s);
	// Initialize the "random" source port number
	static void socketPortRand(uint16_t n);