Replace two naked references of 'std::' with the macro '_VSTD::'. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@236593 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/unordered_map b/include/unordered_map
index 3190ddf..51635de 100644
--- a/include/unordered_map
+++ b/include/unordered_map
@@ -551,7 +551,7 @@
 
     _LIBCPP_INLINE_VISIBILITY
     __hash_value_type(__hash_value_type&& __v)
-        : __nc(std::move(__v.__nc)) {}
+        : __nc(_VSTD::move(__v.__nc)) {}
 
     _LIBCPP_INLINE_VISIBILITY
     __hash_value_type& operator=(const __hash_value_type& __v)
@@ -559,7 +559,7 @@
 
     _LIBCPP_INLINE_VISIBILITY
     __hash_value_type& operator=(__hash_value_type&& __v)
-        {__nc = std::move(__v.__nc); return *this;}
+        {__nc = _VSTD::move(__v.__nc); return *this;}
 
     _LIBCPP_INLINE_VISIBILITY
     ~__hash_value_type() {__cc.~value_type();}