Implement C++17 <variant>. Patch from Michael Park!

This patch was reviewed as https://reviews.llvm.org/D23263.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@288547 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/utilities/variant/version.pass.cpp

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <variant>
+
+#include <variant>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main()
+{
+}