Remove several unused forward declarations. Fixes PR22605.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@229728 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/__hash_table b/include/__hash_table
index 71cf5fb..71b12b3 100644
--- a/include/__hash_table
+++ b/include/__hash_table
@@ -85,8 +85,6 @@
 template <class _ConstNodePtr> class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
 template <class _HashIterator> class _LIBCPP_TYPE_VIS_ONLY __hash_map_iterator;
 template <class _HashIterator> class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator;
-template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
-    class _LIBCPP_TYPE_VIS_ONLY unordered_map;
 
 template <class _NodePtr>
 class _LIBCPP_TYPE_VIS_ONLY __hash_iterator
diff --git a/include/__tree b/include/__tree
index 401891b..d768b38 100644
--- a/include/__tree
+++ b/include/__tree
@@ -28,14 +28,6 @@
     class _LIBCPP_TYPE_VIS_ONLY __tree_iterator;
 template <class _Tp, class _ConstNodePtr, class _DiffType>
     class _LIBCPP_TYPE_VIS_ONLY __tree_const_iterator;
-template <class _Key, class _Tp, class _Compare, class _Allocator>
-    class _LIBCPP_TYPE_VIS_ONLY map;
-template <class _Key, class _Tp, class _Compare, class _Allocator>
-    class _LIBCPP_TYPE_VIS_ONLY multimap;
-template <class _Key, class _Compare, class _Allocator>
-    class _LIBCPP_TYPE_VIS_ONLY set;
-template <class _Key, class _Compare, class _Allocator>
-    class _LIBCPP_TYPE_VIS_ONLY multiset;
 
 /*
 
diff --git a/include/iterator b/include/iterator
index 05d7412..04ff4c1 100644
--- a/include/iterator
+++ b/include/iterator
@@ -1112,8 +1112,6 @@
 >::type
 __unwrap_iter(__wrap_iter<_Tp*>);
 
-template <class _Tp, class _Alloc> class _LIBCPP_TYPE_VIS_ONLY vector;
-
 template <class _Iter>
 class __wrap_iter
 {
@@ -1243,7 +1241,7 @@
 
     template <class _Up> friend class __wrap_iter;
     template <class _CharT, class _Traits, class _Alloc> friend class basic_string;
-    template <class _Tp, class _Alloc> friend class vector;
+    template <class _Tp, class _Alloc> friend class _LIBCPP_TYPE_VIS_ONLY vector;
 
     template <class _Iter1, class _Iter2>
     friend