added equality comparison to reference

doc/unordered/concurrent_flat_map.adoc

@@ -258,6 +258,15 @@ namespace boost {
                         Hash, Allocator)
       -> concurrent_flat_map<Key, T, Hash, std::equal_to<Key>, Allocator>;
 
+  // Equality Comparisons
+  template<class Key, class T, class Hash, class Pred, class Alloc>
+    bool xref:#concurrent_flat_map_operator[operator==](const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& x,
+                    const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& y);
+
+  template<class Key, class T, class Hash, class Pred, class Alloc>
+    bool xref:#concurrent_flat_map_operator_2[operator!=](const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& x,
+                    const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& y);
+
   // swap
   template<class Key, class T, class Hash, class Pred, class Alloc>
     void xref:#concurrent_flat_map_swap_2[swap](concurrent_flat_map<Key, T, Hash, Pred, Alloc>& x,
@@ -1339,6 +1348,38 @@ template<class InputIterator>
     std::tuple_element_t<1, xref:#concurrent_map_iter_value_type[__iter-value-type__]<InputIterator>>>; // exposition only
 -----
 
+=== Equality Comparisons
+
+==== operator==
+```c++
+template<class Key, class T, class Hash, class Pred, class Alloc>
+  bool operator==(const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& x,
+                  const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& y);
+```
+
+Returns `true` if `x.size() == y.size()` and for every element in `x`, there is an element in `y` with the same key, with an equal value (using `operator==` to compare the value types).
+
+[horizontal]
+Concurrency:;; Blocking on `x` and `y`.
+Notes:;; Behavior is undefined if the two tables don't have equivalent equality predicates.
+
+---
+
+==== operator!=
+```c++
+template<class Key, class T, class Hash, class Pred, class Alloc>
+  bool operator!=(const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& x,
+                  const concurrent_flat_map<Key, T, Hash, Pred, Alloc>& y);
+```
+
+Returns `false` if `x.size() == y.size()` and for every element in `x`, there is an element in `y` with the same key, with an equal value (using `operator==` to compare the value types).
+
+[horizontal]
+Concurrency:;; Blocking on `x` and `y`.
+Notes:;; Behavior is undefined if the two tables don't have equivalent equality predicates.
+
+---
+
 === Swap
 ```c++
 template<class Key, class T, class Hash, class Pred, class Alloc>