Nico Rieck:  this patch series fixes visibility issues on Windows as explained in <http://lists.cs.uiuc.edu/pipermail/cfe-dev/2013-August/031214.html>.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@188192 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/cstddef b/include/cstddef
index c263772..7ef16ff 100644
--- a/include/cstddef
+++ b/include/cstddef
@@ -56,7 +56,7 @@
 
 #ifdef _LIBCPP_HAS_NO_NULLPTR
 
-struct _LIBCPP_TYPE_VIS nullptr_t
+struct _LIBCPP_TYPE_VIS_ONLY nullptr_t
 {
     void* __lx;