GitLab

Simplify the return type of CLet internally.
  (No need to construct a list of variable/scheme pairs.)
  (A list of schemes suffices.)
Simplify the return types of [letr1] and [letrn],
  for uniformity with [let1] and [letn].
Add comments in client/Infer.ml
  at a use of [letr1] that needs fixing (I think).