Modified proofs for (q)split, fst, snd for new definitions. The rule f(q)splitE is now called (q)splitE and is weaker than before. The rule '(q)split' is now a meta-equality; this required modifying all proofs involving e.g. split RS trans.

Changed to use split instead of fsplit. The weakening of fsplitE appears not to affect existing proofs.

prove_case_equation now calls uses meta_eq_to_obj_eq to cope with new form of 'split'. Tried calling simp_tac instead of using resolution with trans, but it was significantly slower: 98.3 secs instead of 91.2 secs for ex/Enum.