wenzelm [Sat, 20 Aug 2011 16:06:27 +0200] rev 44331
clarified fulfill_norm_proof: no join_thms yet;
clarified priority of fulfill_proof_future, which is followed by explicit join_thms;
explicit Thm.future_body_of without join yet;
tuned Thm.future_result: join_promises without fulfill_norm_proof;