adds missing file

Author: cjdb

libcxx/test/std/algorithms/alg.nonmodifying/alg.fold/requirements.h

@@ -24,6 +24,7 @@ struct bad_iterator_category {
 };
 
 struct non_movable {
+  non_movable()              = default;
   non_movable(non_movable&&) = delete;
 };
 
@@ -41,6 +42,7 @@ struct copyable_non_movable {
 };
 
 struct non_copy_constructible_callable {
+  non_copy_constructible_callable()                                       = default;
   non_copy_constructible_callable(non_copy_constructible_callable&&)      = default;
   non_copy_constructible_callable(non_copy_constructible_callable const&) = delete;