[libcxx] [test] Replace _LIBCPP_STD_VER with TEST_STD_VER.

This replaces every occurrence of _LIBCPP_STD_VER in the tests with
TEST_STD_VER. Additionally, for every affected
file, #include "test_macros.h" is being added explicitly if it wasn't
already there.

https://reviews.llvm.org/D26294

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@286007 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/tuple/tuple.tuple/tuple.cnstr/copy.pass.cpp

@@ -19,6 +19,8 @@
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
 struct Empty {};
 
 int main()
@@ -50,7 +52,7 @@ int main()
         assert(std::get<1>(t) == 'a');
         assert(std::get<2>(t) == "some text");
     }
-#if _LIBCPP_STD_VER > 11
+#if TEST_STD_VER > 11
     {
         typedef std::tuple<int> T;
         constexpr T t0(2);