Andrei Borzenkov authored Jan 27, 2023 and Marge Bot committed Mar 21, 2023

This patch implements a part of GHC Proposal #475.
The key change is in GHC.Tuple.Prim:

  - data () = ()
  - data (a,b) = (a,b)
  - data (a,b,c) = (a,b,c)
  ...
  + data Unit = ()
  + data Tuple2 a b = (a,b)
  + data Tuple3 a b c = (a,b,c)
  ...

And the rest of the patch makes sure that Unit and Tuple<n>
are pretty-printed as () and (,,...,,) in various contexts.

Updates the haddock submodule.

Co-authored-by: Vladislav Zavialov <vlad.z.4096@gmail.com>