Goal:
  
  A : Type
  P : A → Type
  x : A
  l : list A
  IHl : All P (List.rev l) → All P l
  X : All P (List.rev (l ++ [x]))
  ============================
   (All P (l ++ [x]))


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrrewrite@0> $1 $2