Commit 2021-07-17 11:26 93a37647

chore(algebra/ring/basic): drop commutativity assumptions from some division lemmas (#8334)

• Removes dvd_neg_iff_dvd, neg_dvd_iff_dvd which duplicated dvd_neg, neg_dvd.
• Generalizes two_dvd_bit0 to non-commutative semirings.
• Generalizes a bunch of lemmas from comm_ring to ring.
• Adds even_neg for ring to replace int.even_neg.