added type global_theory -- theory or local_theory;
added begin/exit_local_theory;
removed theory_context;
renamed body_context_node to presentation_context;
removed copy (checkpoint twice instead -- avoids unrelated theories);
(* Title: HOL/Prolog/ROOT.ML
ID: $Id$
Author: David von Oheimb (based on a lecture on Lambda Prolog by Nadathur)
*)
use_thy"Test";
use_thy"Type";