Fix for issue 62, adding DHCP support. New begin() method added to EthernetClass which takes just a MAC address and gets the rest of its configuration information via DHCP. Examples updated to use the IPAddress class and some have been changed to get their config via DHCP.

libraries/Ethernet/IPAddress.cpp

@@ -37,3 +37,8 @@ IPAddress& IPAddress::operator=(uint32_t address)
     return *this;
 }
 
+bool IPAddress::operator==(const uint8_t* addr)
+{
+    return memcmp(addr, _address, sizeof(_address)) == 0;
+}
+