[iterator.synopsis] Fix indexing targets for singular sentinels. (#4030)

Author: jensmaurer

source/iterators.tex

@@ -30,8 +30,6 @@
 \rSec1[iterator.synopsis]{Header \tcode{<iterator>}\ synopsis}
 
 \indexheader{iterator}%
-\indexlibraryglobal{default_sentinel}%
-\indexlibraryglobal{unreachable_sentinel}%
 \begin{codeblock}
 #include <compare>              // see \ref{compare.syn}
 #include <concepts>             // see \ref{concepts.syn}
@@ -381,7 +379,7 @@
 
   // \ref{default.sentinels}, default sentinels
   struct default_sentinel_t;
-  inline constexpr default_sentinel_t default_sentinel{};
+  inline constexpr default_sentinel_t @\libglobal{default_sentinel}@{};
 
   // \ref{iterators.counted}, counted iterators
   template<@\libconcept{input_or_output_iterator}@ I> class counted_iterator;
@@ -394,7 +392,7 @@
 
   // \ref{unreachable.sentinels}, unreachable sentinels
   struct unreachable_sentinel_t;
-  inline constexpr unreachable_sentinel_t unreachable_sentinel{};
+  inline constexpr unreachable_sentinel_t @\libglobal{unreachable_sentinel}@{};
 
   // \ref{stream.iterators}, stream iterators
   template<class T, class charT = char, class traits = char_traits<charT>,