[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/containers/associative/set/iterator.pass.cpp

@@ -29,6 +29,7 @@
 #include <set>
 #include <cassert>
 
+#include "test_macros.h"
 #include "min_allocator.h"
 
 int main()
@@ -191,7 +192,7 @@ int main()
             assert(*i == j);
     }
 #endif
-#if _LIBCPP_STD_VER > 11
+#if TEST_STD_VER > 11
     { // N3644 testing
         typedef std::set<int> C;
         C::iterator ii1{}, ii2{};