libstdc++: Use C++98 syntax to instantiate input_iterator_tag

	* include/debug/helper_functions.h (__valid_range_aux): Use C++98
	std::input_iterator_tag default constructor invocation.

From-SVN: r278731

libstdc++-v3/ChangeLog

 2019-11-26  François Dumont  <fdumont@gcc.gnu.org>
 
+	* include/debug/helper_functions.h (__valid_range_aux): Use C++98
+	std::input_iterator_tag default constructor invocation.
+
 	* include/debug/array (array<>::fill): Add C++20 constexpr.
 	(array<>::swap): Likewise.
 

libstdc++-v3/include/debug/helper_functions.h

@@ -168,7 +168,7 @@ namespace __gnu_debug
 		      std::random_access_iterator_tag)
     {
       return
-	__valid_range_aux(__first, __last, std::input_iterator_tag{})
+	__valid_range_aux(__first, __last, std::input_iterator_tag())
 	&& __first <= __last;
     }
 
@@ -192,7 +192,7 @@ namespace __gnu_debug
 		      typename _Distance_traits<_InputIterator>::__type& __dist,
 		      std::__false_type)
     {
-      if (!__valid_range_aux(__first, __last, std::input_iterator_tag{}))
+      if (!__valid_range_aux(__first, __last, std::input_iterator_tag()))
 	return false;
 
       __dist = __get_distance(__first, __last);