Fix or move various non-standard tests.

This patch does the following:

* Remove <__config> includes from some container tests.
* Guards uses of std::launch::any in async tests because it's an extension.
* Move "test/std/extensions" to "test/libcxx/extensions"
* Moves various non-standard tests including those in "sequences/vector",
  "std/localization" and "utilities/meta".


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@267981 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/extensions/nothing_to_do.pass.cpp

@@ -0,0 +1,12 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+int main()
+{
+}