Updated all serial in setup examples with a note about the serial check

libraries/Ethernet/examples/DhcpChatServer/DhcpChatServer.ino

@@ -37,7 +37,9 @@ boolean gotAMessage = false; // whether or not you got a message from the client
 void setup() {
   // Open serial communications and wait for port to open:
   Serial.begin(9600);
-  while(!Serial) ;
+  // this check is only needed on the Leonardo:
+  while (!Serial) ;
+ ;
 
   // start the Ethernet connection:
   Serial.println("Trying to get an IP address using DHCP");