Implement LWG#2566: Requirements on the first template parameter of container adaptors

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@263450 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/stack b/include/stack
index 2992b09..64fd652 100644
--- a/include/stack
+++ b/include/stack
@@ -112,7 +112,8 @@
     typedef typename container_type::reference       reference;
     typedef typename container_type::const_reference const_reference;
     typedef typename container_type::size_type       size_type;
-
+    static_assert((is_same<_Tp, value_type>::value), "" );
+    
 protected:
     container_type c;