Rename ___make_pair_return to __make_pair_return_impl; ___make_tuple_return to __make_tuple_return_impl; and ____iterator_traits to __iterator_traits_impl. Part of a campaign to remove > 2 underscores from libc++. No functionality change.

llvm-svn: 198457
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 0724bf67672c754aa61ce2659939450ff22c30fa
diff --git a/include/tuple b/include/tuple
index a1a7bcf..24e086d 100644
--- a/include/tuple
+++ b/include/tuple
@@ -816,13 +816,13 @@
 template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY reference_wrapper;
 
 template <class _Tp>
-struct ___make_tuple_return
+struct __make_tuple_return_impl
 {
     typedef _Tp type;
 };
 
 template <class _Tp>
-struct ___make_tuple_return<reference_wrapper<_Tp> >
+struct __make_tuple_return_impl<reference_wrapper<_Tp> >
 {
     typedef _Tp& type;
 };
@@ -830,7 +830,7 @@
 template <class _Tp>
 struct __make_tuple_return
 {
-    typedef typename ___make_tuple_return<typename decay<_Tp>::type>::type type;
+    typedef typename __make_tuple_return_impl<typename decay<_Tp>::type>::type type;
 };
 
 template <class... _Tp>