[libc++] Add missing friend keyword
Otherwise, we're declaring a non-static member function, and that
gives errors in C++11 because of the change of semantics between
C++11 and C++14 for non-const constexpr member functions.
This was always intended to be a friend declaration.
diff --git a/libcxx/include/iterator b/libcxx/include/iterator
index 45516db..e2910e9 100644
--- a/libcxx/include/iterator
+++ b/libcxx/include/iterator
@@ -1618,7 +1618,7 @@
__unwrap_iter(__wrap_iter<_Tp*>);
#else
template <class _Tp>
- inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR friend
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
