[libcxx] deprecates/removes std::raw_storage_iterator

C++17 deprecates `std::raw_storage_iterator` and C++20 removes it.

Implements part of:
  * P0174R2 'Deprecating Vestigial Library Parts in C++17'
  * P0619R4 'Reviewing Deprecated Facilities of C++17 for C++20'

Differential Revision: https://reviews.llvm.org/D101730

Author: cjdb

libcxx/include/__memory/raw_storage_iterator.h

@@ -25,8 +25,10 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#if _LIBCPP_STD_VER <= 17
+
 template <class _OutputIterator, class _Tp>
-class _LIBCPP_TEMPLATE_VIS raw_storage_iterator
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 raw_storage_iterator
     : public iterator<output_iterator_tag,
                       _Tp,                                         // purposefully not C++03
                       ptrdiff_t,                                   // purposefully not C++03
@@ -52,6 +54,8 @@ class _LIBCPP_TEMPLATE_VIS raw_storage_iterator
 #endif
 };
 
+#endif // _LIBCPP_STD_VER <= 17
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

libcxx/test/std/utilities/memory/storage.iterator/deprecated.verify.cpp

@@ -0,0 +1,16 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: c++17
+
+// std::raw_storage_iterator
+
+#include <memory>
+
+std::raw_storage_iterator<int*, int> it(nullptr);
+// expected-warning@-1{{'raw_storage_iterator<int *, int>' is deprecated}}

libcxx/test/std/utilities/memory/storage.iterator/raw_storage_iterator.base.pass.cpp

@@ -6,8 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+// REQUIRES: c++03 || c++11 || c++14 || c++17
+
 // raw_storage_iterator
 
+#define _LIBCPP_DISABLE_DEPRECATION_WARNINGS
+
 #include <memory>
 #include <type_traits>
 #include <cassert>

libcxx/test/std/utilities/memory/storage.iterator/raw_storage_iterator.pass.cpp

@@ -6,8 +6,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+// REQUIRES: c++03 || c++11 || c++14 || c++17
+
 // raw_storage_iterator
 
+#define _LIBCPP_DISABLE_DEPRECATION_WARNINGS
+
 #include <memory>
 #include <type_traits>
 #include <cassert>