Tweak the type signature for scanl and scanr.

It is convenient for Coq extraction for the constant 1 factor
to be on the left of the addition symbol.

lib/Cryptol.cry

@@ -1158,12 +1158,12 @@ product xs = foldl' (*) (fromInteger 1) xs
 /**
  * Scan left is like a foldl that also emits the intermediate values.
  */
-primitive scanl : {n, a, b}  (a -> b -> a) -> a -> [n]b -> [n+1]a
+primitive scanl : {n, a, b}  (a -> b -> a) -> a -> [n]b -> [1+n]a
 
 /**
  * Scan right is like a foldr that also emits the intermediate values.
  */
-scanr : {n, a, b} (fin n) => (a -> b -> b) -> b -> [n]a -> [n+1]b
+scanr : {n, a, b} (fin n) => (a -> b -> b) -> b -> [n]a -> [1+n]b
 scanr f acc xs = reverse (scanl (\a b -> f b a) acc (reverse xs))
 
 /**

src/Cryptol/Eval/Generic.hs

@@ -1814,7 +1814,7 @@ foldl'V sym =
        go1 f a' bs
 
 
--- scanl : {n, a, b}  (a -> b -> a) -> a -> [n]b -> [n+1]a
+-- scanl : {n, a, b}  (a -> b -> a) -> a -> [n]b -> [1+n]a
 scanlV :: forall sym. Backend sym => sym -> Prim sym
 scanlV sym =
   PNumPoly \n ->