remove obsoleted unary_function inheritance

Author: fmauger

source/bxdatatools/include/datatools/event_id.h

@@ -217,7 +217,7 @@ namespace datatools {
   /** May be used with the std::find_if standard algorithm.
    */
   class event_id_equal_predicate
-    : public std::unary_function<event_id, bool>
+  //  : public std::unary_function<event_id, bool>
   {
   public:
 

source/bxdatatools/include/datatools/i_predicate.h

@@ -3,14 +3,15 @@
 #define DATATOOLS_I_PREDICATE_H
 
 // Standard Library:
-#include<functional>
+// #include <functional>
 
 namespace datatools {
 
   //! \brief A template predicate abstract class
   template <class T>
   class i_predicate
-    : public std::unary_function<const T&, bool>
+	// obsoleted from C++17
+	// : public std::unary_function<const T&, bool>
   {
   public:
     virtual bool operator()(const T & obj_) const = 0;

source/bxdatatools/include/datatools/smart_ref.h

@@ -119,7 +119,7 @@ namespace datatools {
 
     //! \brief Predicate used by the smart_ref template class
     class has_flag
-      : public std::unary_function<smart_ref_type, bool>
+    //  : public std::unary_function<smart_ref_type, bool>
     {
     public: