Merge in commit 73375c3 from upstream

Replace `peek()` with `available()` during connection status check to avoid losing messages.

Closes adafruit#22.

arduino/libraries/WiFi/src/WiFiClient.cpp

@@ -177,8 +177,7 @@ void WiFiClient::stop()
 uint8_t WiFiClient::connected()
 {
   if (_socket != -1) {
-    // use peek to update socket state
+    available();
-    peek();
   }
 
   return (_socket != -1);