Now depends upon Bool, so that 1 and 2 are defined

Moved theorems Ord_cases_lemma and Ord_cases here from Univ, strengthening the succ(j) case to include Ord(j). Proved trans_induct3, le_implies_UN_le_UN, Ord_1, lt_Ord2, le_Ord2.

Added constants Ord_alt, ++, **

Proved equivalence of Ord and Ord_alt. Proved ordertype_eq_imp_ord_iso, le_well_ord_Memrel, le_ordertype_Memrel, lt_oadd1, oadd_le_self, bij_0_sum, oadd_0, oadd_assoc, id_ord_iso_Memrel, ordertype_0. Now well_ord_Memrel follows from le_well_ord_Memrel and ordertype_Memrel follows from le_ordertype_Memrel. Proved simpler versions of Krzysztof's theorems Ord_oadd, ordertype_pred_subset, ordertype_pred_lt, ordertype_pred_unfold, bij_sum_0, bij_sum_succ, ordertype_sum_Memrel, lt_oadd_disj, oadd_inject. Deleted ordertype_subset: subsumed by ordertype_pred_unfold. Proved ordinal multiplication theorems Ord_omult, lt_omult, omult_oadd_lt, omult_unfold, omult_0, omult_0_left, omult_1, omult_1_left, oadd_omult_distrib, omult_succ, omult_assoc, omult_UN, omult_Limit, lt_omult1, omult_le_self, omult_le_mono1, omult_lt_mono2, omult_le_mono2, omult_le_mono, omult_lt_mono, omult_le_self2, omult_inject.

Proved ord_isoI, ord_iso_refl. Simplified proof of ord_iso_restrict_pred. Proved theorems irrefl_0, ..., well_ord_0.

Proved cadd_cmult_distrib.

Now proof of Ord_jump_cardinal uses ordertype_pred_unfold; proof of sum_0_eqpoll uses bij_0_sum; proof of sum_0_eqpoll uses sum_prod_distrib_bij; proof of sum_assoc_eqpoll uses sum_assoc_bij; proof of prod_assoc_eqpoll uses prod_assoc_bij. Proved well_ord_cadd_cmult_distrib.

Added Krzysztof's theorem LeastI2. Proof of sum_eqpoll_cong uses lemma sum_bij; proof of prod_eqpoll_cong uses lemma prod_bij.

pretty_gram: now sorts productions;

removed print_sign, print_axioms;