Write natvis for foa and cfoa containers

include/boost/unordered/detail/foa/core.hpp

@@ -1413,6 +1413,12 @@ __declspec(empty_bases) /* activate EBO with multiple inheritance */
 
 table_core:empty_value<Hash,0>,empty_value<Pred,1>,empty_value<Allocator,2>
 {
+private:
+  // These `baseN` aliases are for debugger visualizations, like natvis
+  using base1=empty_value<Hash,0>;
+  using base2=empty_value<Pred,1>;
+  using base3=empty_value<Allocator,2>;
+
 public:
   using type_policy=TypePolicy;
   using group_type=Group;