Added [simp]-lemmas "in_inv_image" and "in_lex_prod" in the spirit of "in_measure".
This simplifies some proofs.
By chapter:
chapters 1 and 2, maybe 3: Peter White
chapters 6, 7 and 8: David von Oheim
chapter 6, maybe 8: Gerwin Klein
chapters 3, maybe 4: Tanja Vos
chapters 1-3 at least: Stefano Bistarelli