[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.rel/lt.pass.cpp

@@ -33,6 +33,8 @@
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
 int main()
 {
     {
@@ -195,7 +197,7 @@ int main()
         assert(!(t1 >  t2));
         assert(!(t1 >= t2));
     }
-#if _LIBCPP_STD_VER > 11
+#if TEST_STD_VER > 11
     {
         typedef std::tuple<char, int, double> T1;
         typedef std::tuple<double, char, int> T2;