Cleanup _LIBCPP_HAS_NO_<c++11-feature> in the input.output library

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@300626 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/input.output/string.streams/stringstream.cons/stringstream.assign/move.pass.cpp

@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: c++98, c++03
+
 // <sstream>
 
 // template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
@@ -19,7 +21,6 @@
 
 int main()
 {
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     {
         std::stringstream ss0(" 123 456 ");
         std::stringstream ss;
@@ -50,5 +51,4 @@ int main()
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 }