[libcxx] Add <experimental/any> v2.

Summary:
This patch adds the second revision of <experimental/any>. 
I've been working from the LFTS draft found at this link. https://rawgit.com/cplusplus/fundamentals-ts/v1/fundamentals-ts.html#any



Reviewers: danalbert, jroelofs, K-ballo, mclow.lists

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D6762

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@243728 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/experimental/any/size_and_alignment.pass.cpp

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11
+
+// <experimental/any>
+
+// Check that the size and alignment of any are what we expect.
+
+#include <experimental/any>
+
+int main()
+{
+    using std::experimental::any;
+    static_assert(sizeof(any) == sizeof(void*)*4, "");
+    static_assert(alignof(any) == alignof(void*), "");
+}