Added virtual bool operator==(const bool value) and virtual bool operator!=(const bool value).

Fixes arduino#2611
Bug introduced with arduino#1700

Author: Federico Fissore

libraries/Ethernet/src/EthernetClient.h

@@ -24,6 +24,8 @@ class EthernetClient : public Client {
   virtual void stop();
   virtual uint8_t connected();
   virtual operator bool();
+  virtual bool operator==(const bool value) { return bool() == value; }
+  virtual bool operator!=(const bool value) { return bool() != value; }
   virtual bool operator==(const EthernetClient&);
   virtual bool operator!=(const EthernetClient& rhs) { return !this->operator==(rhs); };