Zhihao Yuan noted that there were a few unneeded  statements.  Eliminated the unnecessary ones, and commented the ones that are there for non-obvious reasons such as to help things limp along in C++03 language mode.

llvm-svn: 189039
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 179b1f8cf2f4b9dc8290c6753bf7626f48a81321
diff --git a/include/__tree b/include/__tree
index 67f0a2b..acf8759 100644
--- a/include/__tree
+++ b/include/__tree
@@ -1854,7 +1854,7 @@
     __node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
     __node_traits::construct(__na, _VSTD::addressof(__h->__value_), __v);
     __h.get_deleter().__value_constructed = true;
-    return _VSTD::move(__h);
+    return _VSTD::move(__h);  // explicitly moved for C++03
 }
 
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES