Dimitry Andric:  many visibility fixes.  Howard:  Much appreciated.  Can you send me a patch to CREDITS.TXT?

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@163862 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__hash_table b/include/__hash_table
index 3c39ac7..ba04b3e 100644
--- a/include/__hash_table
+++ b/include/__hash_table
@@ -80,9 +80,9 @@
 }
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc> class __hash_table;
-template <class _ConstNodePtr> class __hash_const_iterator;
-template <class _HashIterator> class __hash_map_iterator;
-template <class _HashIterator> class __hash_map_const_iterator;
+template <class _ConstNodePtr> class _LIBCPP_VISIBLE __hash_const_iterator;
+template <class _HashIterator> class _LIBCPP_VISIBLE __hash_map_iterator;
+template <class _HashIterator> class _LIBCPP_VISIBLE __hash_map_const_iterator;
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
     class _LIBCPP_VISIBLE unordered_map;