Quash a whole bunch of warnings

llvm-svn: 145624
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: c206366fd7774aff222578c2680b931a4c2c35ba
diff --git a/include/__tuple b/include/__tuple
index 15193b4..3b2be1c 100644
--- a/include/__tuple
+++ b/include/__tuple
@@ -65,7 +65,7 @@
 };
 
 template <class ..._Tp> class _LIBCPP_VISIBLE tuple;
-template <class _T1, class _T2> class _LIBCPP_VISIBLE pair;
+template <class _T1, class _T2> struct _LIBCPP_VISIBLE pair;
 template <class _Tp, size_t _Size> struct _LIBCPP_VISIBLE array;
 
 template <class _Tp> struct __tuple_like : false_type {};