some more stuff for the avl tree

bintree.h

@@ -426,6 +426,10 @@ public:
     return node;
   }
 
+  inline
+  bool in_tree(Node* node)
+  { return (node->tree == this); }
+
   #ifdef DUMP
   void dump()
   {
@@ -452,9 +456,13 @@ public:
   { Base::remove(static_cast<typename Base::Node*>(node)); }
 
   inline
-  T* find(Key_type key)
+  T* lookup(Key_type key)
   { return static_cast<T*>(Base::lookup(key)); }
 
+  inline
+  bool in_tree(T* node)
+  { return Base::in_tree(static_cast<Base::Node*>(node)); }
+
   #ifdef DUMP
   inline
   void dump()