Note [Record selectors]

Record selectors are injected as ordianry functions definitions, very
early in the pipeline.

* `mkRecSelBinds` produces /un-typechecked/ bindings, rather like 'deriving'
   This makes life easier, because the later type checking will add
   all necessary type abstractions and applications; and handling for
   UNPACK pragmas etc

* Record selectors are not treated as "implicit".  See
  See Note [Implicit TyThings] in GHC.Types.TyThing and
      Note [Injecting implicit bindings] in GHC.CoreToStg.AddImplicitBinds