Added HWAddress<>::is_broadcast.

include/hw_address.h

@@ -227,6 +227,13 @@ public:
         return address_size;
     }
     
+    /**
+     * \brief Indicates whether this is a broadcast address
+     */
+    bool is_broadcast() const {
+        return *std::min_element(begin(), end()) == 0xff;
+    }
+    
     /**
      * \brief Convert this address to a hex-notation std::string address.
      *