eliminate unused parameter warning

include/sync-digest.h

@@ -118,7 +118,7 @@ public:
   
 private:
   Digest &
-  operator = (Digest &digest) { return *this; }
+  operator = (Digest &digest) { (void)digest; return *this; }
   
   /**
    * @brief Add size bytes of buffer to the hash

include/sync-std-name-info.h

@@ -63,7 +63,7 @@ private:
    * @brief Disabled default
    */
   StdNameInfo () {}
-  StdNameInfo& operator = (const StdNameInfo &info) { return *this; }
+  StdNameInfo& operator = (const StdNameInfo &info) { (void)info; return *this; }
   StdNameInfo (const std::string &name);
   
   std::string m_name;