N3644 support for <string> and <vector>

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@187909 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/iterator b/include/iterator
index 4989d8b..858510d 100644
--- a/include/iterator
+++ b/include/iterator
@@ -1093,6 +1093,9 @@
     iterator_type __i;
 public:
     _LIBCPP_INLINE_VISIBILITY __wrap_iter() _NOEXCEPT
+#if _LIBCPP_STD_VER > 11
+                : __i{}
+#endif
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         __get_db()->__insert_i(this);