Simprocs for type "nat" no longer introduce numerals unless they are already
present in the expression, and in a coefficient position (i.e. as a factor
of a monomial).
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