Fix recent build errors

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@292689 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/memory/util.smartptr/util.smartptr.hash/hash_unique_ptr.pass.cpp

@@ -46,13 +46,16 @@ void test_disabled_with_deleter() {
   test_hash_disabled_for_type<pointer>();
 }
 
+namespace std {
+
 template <class T>
-struct std::hash<min_pointer<T, std::integral_constant<size_t, 1>>> {
-  size_t operator()(min_pointer<T, std::integral_constant<size_t, 1>> p) const {
+struct hash<::min_pointer<T, std::integral_constant<size_t, 1>>> {
+  size_t operator()(::min_pointer<T, std::integral_constant<size_t, 1>> p) const {
     if (!p) return 0;
     return std::hash<T*>{}(std::addressof(*p));
   }
 };
+}
 
 struct A {};