[iterator.synopsis] Add 'freestanding' markers per P1642R11

Author: jensmaurer

source/iterators.tex

@@ -335,12 +335,12 @@
 
   // \ref{const.iterators}, constant iterators and sentinels
   template<@\libconcept{indirectly_readable}@ I>
-    using iter_const_reference_t = @\seebelow@;
+    using iter_const_reference_t = @\seebelow@;           // freestanding
   template<class Iterator>
     concept @\exposconcept{constant-iterator}@ = @\seebelow@; // \expos
 
   template<class Iterator>
-    class basic_const_iterator;
+    class basic_const_iterator;                         // freestanding
 
   template<class T, @\libconcept{common_with}@<T> U>
   struct common_type<basic_const_iterator<T>, U> {
@@ -356,16 +356,16 @@
   };
 
   template<@\libconcept{input_iterator}@ I>
-    using const_iterator = @\seebelow@;
+    using const_iterator = @\seebelow@;                       // freestanding
 
   template<class S>
-    using const_sentinel = @\seebelow@;
+    using const_sentinel = @\seebelow@;                       // freestanding
 
   template<@\libconcept{input_iterator}@ I>
-    constexpr const_iterator<I> make_const_iterator(I it) { return it; }
+    constexpr const_iterator<I> make_const_iterator(I it) { return it; }    // freestanding
 
   template<class S>
-    constexpr const_sentinel<S> make_const_sentinel(S s) { return s; }
+    constexpr const_sentinel<S> make_const_sentinel(S s) { return s; }      // freestanding
 
   // \ref{move.iterators}, move iterators and sentinels
   template<class Iterator> class move_iterator;