_STD -> _VSTD to avoid macro clash on windows

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@134190 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/istream b/include/istream
index b427605..024f5ce 100644
--- a/include/istream
+++ b/include/istream
@@ -321,7 +321,7 @@
 void
 basic_istream<_CharT, _Traits>::swap(basic_istream& __rhs)
 {
-    _STD::swap(__gc_, __rhs.__gc_);
+    _VSTD::swap(__gc_, __rhs.__gc_);
     basic_ios<char_type, traits_type>::swap(__rhs);
 }
 
@@ -1273,7 +1273,7 @@
             case 0:
                 break;
             default:
-                __c = _STD::min(__c, __n);
+                __c = _VSTD::min(__c, __n);
                 for (streamsize __k = 0; __k < __c; ++__k, ++__s, ++__i)
                     *__s = *__i;
             }
@@ -1527,7 +1527,7 @@
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_iostream<_CharT, _Traits>::basic_iostream(basic_iostream&& __rhs)
-    : basic_istream<_CharT, _Traits>(_STD::move(__rhs))
+    : basic_istream<_CharT, _Traits>(_VSTD::move(__rhs))
 {
 }