remove preliminary file

src/prolog/rc_atom.rs

@@ -1,11 +0,0 @@
-use prolog::ast::*;
-
-use std::cell::RefCell;
-use std::rc::Rc;
-
-pub type TabledData<T> = HashSet<Rc<T>>
-    
-pub struct TabledRc<T> {
-    atom: Rc<T>,
-    table: Rc<RefCell<TabledData<T>>>
-}