[libcxx] expose experimental::erased_type for all standard versions.

[EricWF]

Summary

The polymorphic allocator implementation would greatly benefit by defining virtual functions in the dynlib instead of inline. In order to do that some types are going to have to be available outside of c++1y. This is the first step.

[EricWF]

Update one more test. Sorry for the spam.

[mclow.lists]

LGTM; please commit.

[EricWF]

Marking as accepted to make arc play nice.

include/experimental/utility

 } // namespace fundamentals_v1
 } // namespace experimental
 } // namespace std
 
  */
 
 # include <experimental/__config>
 
-#if _LIBCPP_STD_VER > 11
-
 # include <utility>
 
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
   struct _LIBCPP_TYPE_VIS_ONLY erased_type { };
 
 _LIBCPP_END_NAMESPACE_LFTS
 
-#endif /* _LIBCPP_STD_VER > 11 */
-
 #endif /* _LIBCPP_EXPERIMENTAL_UTILITY */

test/experimental/utilities/utility/utility.erased.type/erased_type.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 // <experimental/utility>
 
 #include <experimental/utility>
 
 int main()
 {
-#if _LIBCPP_STD_VER > 11
-    using std::experimental::erased_type;
-    constexpr erased_type e{};
-#endif
+    std::experimental::erased_type e();
 }

test/experimental/utilities/utility/utility.synop/includes.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 // <experimental/utility>
 
 #include <experimental/utility>
 
-int main()
-{
-#if _LIBCPP_STD_VER > 11
-# ifndef _LIBCPP_UTILITY
+#ifndef _LIBCPP_UTILITY
 #   error "<experimental/utility> must include <utility>"
-# endif
-#endif /* _LIBCPP_STD_VER > 11 */
+#endif
+
+int main()
+{
 }