implement arduinos clienth and a few small changes to support it

Allows reuse of most existing client based code with VERY few changes. Selfishly I'm trying to port a websocket project I maintain called SkynetIM and I need this to avoid heavy alteration for Spark support. 

Tested server with the note from this commit
https://github.com/spark/core-firmware/commit/0cd736d21c789524d86601779589693b3debe939

And client with the arduino ethernet example altered for spark below:

```cpp
 #include "application.h"

// if you don't want to use DNS (and reduce your sketch size)
// use the numeric IP instead of the name for the server:
//IPAddress server(74,125,232,128);  // numeric IP for Google (no DNS)
char server[] = "www.google.com";    // name address for Google (using DNS)

// Set the static IP address to use if the DHCP fails to assign
IPAddress ip(192, 168, 0, 177);

TCPClient client;

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);

  Serial.println("connecting...");

  // if you get a connection, report back via serial:
  if (client.connect(server, 80)) {
    Serial.println("connected");
    // Make a HTTP request:
    client.println("GET /search?q=arduino HTTP/1.1");
    client.println("Host: www.google.com");
    client.println("Connection: close");
    client.println();
  }
  else {
    // kf you didn't get a connection to the server:
    Serial.println("connection failed");
  }
}

void loop()
{
  // if there are incoming bytes available
  // from the server, read them and print them:
  if (client.available()) {
    char c = client.read();
    Serial.print(c);
  }

  // if the server's disconnected, stop the client:
  if (!client.connected()) {
    Serial.println();
    Serial.println("disconnecting.");
    client.stop();

    // do nothing forevermore:
    while (true);
  }
}
```