[libc++] Use UNSUPPORTED instead of TEST_STD_VER #ifdef

When the whole test only works starting at some version of the Standard,
use UNSUPPORTED lit markup instead of #ifdef TEST_STD_VER. This provides
more visibility into the test suite.

Reviewed as https://reviews.llvm.org/D57704.
Thanks to Andrey Maksimov for the patch.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@353206 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/tuple/tuple.tuple/TupleFunction.pass.cpp

@@ -6,12 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: c++98, c++03
+
 // This is for bugs 18853 and 19118
 
-#include "test_macros.h"
-
-#if TEST_STD_VER >= 11
-
 #include <tuple>
 #include <functional>
 
@@ -32,6 +30,3 @@ int main(int, char**)
 
   return 0;
 }
-#else
-int main(int, char**) { return 0; }
-#endif