[PATCH][_Hashtable] Add missing destructor call

[François Dumont]

Noticed looking for other occasion to replace __try/__catch with RAII 
helper.

    libstdc++: [_Hashtable] Add missing node destructor call
    libstdc++-v3/ChangeLog:

            * include/bits/hashtable_policy.h
            (_Hashtable_alloc<>::_M_allocate_node): Add missing call to 
node destructor
            on construct exception.

Tested under Linux x64, ok to commit ?

I hope gmail appli will appreciate .diff instead of .patch. .txt are not 
in .gitignore so annoying to use for patches.

François
diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h
index 2d13bda6ae0..ed2b2c02a4a 100644
--- a/libstdc++-v3/include/bits/hashtable_policy.h
+++ b/libstdc++-v3/include/bits/hashtable_policy.h
@@ -2020,19 +2020,20 @@ namespace __detail
       _Hashtable_alloc<_NodeAlloc>::_M_allocate_node(_Args&&... __args)
       -> __node_ptr
       {
-	auto __nptr = __node_alloc_traits::allocate(_M_node_allocator(), 1);
+	auto& __alloc = _M_node_allocator();
+	auto __nptr = __node_alloc_traits::allocate(__alloc, 1);
 	__node_ptr __n = std::__to_address(__nptr);
 	__try
 	  {
 	    ::new ((void*)__n) __node_type;
-	    __node_alloc_traits::construct(_M_node_allocator(),
-					   __n->_M_valptr(),
+	    __node_alloc_traits::construct(__alloc, __n->_M_valptr(),
 					   std::forward<_Args>(__args)...);
 	    return __n;
 	  }
 	__catch(...)
 	  {
-	    __node_alloc_traits::deallocate(_M_node_allocator(), __nptr, 1);
+	    __n->~__node_type();
+	    __node_alloc_traits::deallocate(__alloc, __nptr, 1);
 	    __throw_exception_again;
 	  }
       }