Document or remove source pragmas

GHC supports several pragmas to be interleaved with expressions, as used with this AST node:

  -- Expressions annotated with pragmas, written as {-# ... #-}
  | HsPragE (XPragE p) (HsPragE p) (LHsExpr p)

Here is the HsPragE type:

data HsPragE p
  = HsPragSCC   ...
  | HsPragCore  ...
  | HsPragTick  ...
  | XHsPragE (XXPragE p)

HsPragSCC feels familiar. I'm worried about the other two possibilities here. GHC parses them:

prag_e :: { Located ([AddAnn], HsPragE GhcPs) }
      : '{-# SCC' STRING '#-}'      { ... }
      | '{-# SCC' VARID  '#-}'      { ... }
      | '{-# GENERATED' STRING INTEGER ':' INTEGER '-' INTEGER ':' INTEGER '#-}'
                                      { ... HsPragTick ... }
      | '{-# CORE' STRING '#-}'
            { ... HsPragCore ... }

Yet the strings CORE and GENERATED (in caps) never appear in the manual.

Are these used? If so, we should document them. If not, we should remove them.