Fix hashtable node deallocation

[François Dumont]

While working on a hashtable enhancement I noticed that we are not using 
the correct method to deallocate node if the constructor throws in 
_ReuseOrAllocNode operator(). I had to introduce a new 
_M_deallocate_node_ptr for that as node value shall not be destroy again.

I also check other places and noticed that a __node_type destructor call 
was missing.

    * include/bits/hashtable_policy.h
(_Hashtable_alloc<>::_M_deallocate_node_ptr(__node_type*)): New.
    (_Hashtable_alloc<>::_M_deallocate_node(__node_type*)): Use latter.
(_ReuseOrAllocNode<>::operator<_Arg>()(_Arg&&)): Likewise.
    (_Hashtable_alloc<>::_M_allocate_node): Add ~__node_type call.

Tested under Linux x86_64.

Ok to commit ?

François

diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h
index d8e8c13858d..c87c65fd9f7 100644
--- a/libstdc++-v3/include/bits/hashtable_policy.h
+++ b/libstdc++-v3/include/bits/hashtable_policy.h
@@ -148,8 +148,7 @@ namespace __detail
 		}
 	      __catch(...)
 		{
-		  __node->~__node_type();
-		  __node_alloc_traits::deallocate(__a, __node, 1);
+		  _M_h._M_deallocate_node_ptr(__node);
 		  __throw_exception_again;
 		}
 	      return __node;
@@ -2116,6 +2115,9 @@ namespace __detail
       void
       _M_deallocate_node(__node_type* __n);
 
+      void
+      _M_deallocate_node_ptr(__node_type* __n);
+
       // Deallocate the linked list of nodes pointed to by __n
       void
       _M_deallocate_nodes(__node_type* __n);
@@ -2146,6 +2148,7 @@ namespace __detail
 	  }
 	__catch(...)
 	  {
+	    __n->~__node_type();
 	    __node_alloc_traits::deallocate(_M_node_allocator(), __nptr, 1);
 	    __throw_exception_again;
 	  }
@@ -2154,10 +2157,17 @@ namespace __detail
   template<typename _NodeAlloc>
     void
     _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node(__node_type* __n)
+    {
+      __node_alloc_traits::destroy(_M_node_allocator(), __n->_M_valptr());
+      _M_deallocate_node_ptr(__n);
+    }
+
+  template<typename _NodeAlloc>
+    void
+    _Hashtable_alloc<_NodeAlloc>::_M_deallocate_node_ptr(__node_type* __n)
     {
       typedef typename __node_alloc_traits::pointer _Ptr;
       auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__n);
-      __node_alloc_traits::destroy(_M_node_allocator(), __n->_M_valptr());
       __n->~__node_type();
       __node_alloc_traits::deallocate(_M_node_allocator(), __ptr, 1);
     }