SAWCore maxNat has the wrong definition

[robdockins]

saw-script/saw-core/prelude/Prelude.sawcore

Lines 860 to 864 in 7d8bf6b

	maxNat : Nat -> Nat -> Nat;
	maxNat x y =
	Nat_cases2 Nat (\ (x':Nat) -> x')
	(\ (y':Nat) -> Succ y')
	(\ (y':Nat) -> \ (x':Nat) -> \ (sub_xy:Nat) -> sub_xy) y x;

This defines the incorrect function. The final case should actually be (Succ sub_xy). The naming makes me suspect this is a copy-paste error from the prior definition of subNat. We mostly haven't noticed this problem because maxNat is overridden in the simulators with a correct definition. However, for Coq extraction, we are directly translating this recursive definition and computing the wrong answers.

[robdockins]

This definition seems like it came in when we refactored SAWCore to use recursors. CF c37aa45