add structural tests for partial strings, rename ast.rs

src/prolog/toplevel.rs

@@ -2,7 +2,7 @@ use prolog_parser::ast::*;
 use prolog_parser::parser::*;
 use prolog_parser::tabled_rc::*;
 
-use prolog::ast::*;
+use prolog::instructions::*;
 use prolog::iterators::*;
 use prolog::machine::*;
 use prolog::num::*;