Fix Haddock comment for Integer datatype
Fix Haddock comment for Integer datatype

Move implementation notes for Integer to Haddock named section

Revert documentation named chunk change [skip ci]

Haddock's named chunk feature was not used correctly in this case,
as it cannot export only parts of a Haddock top level comment.

As such, it was removed and replaced by a message informing the end-
user to browse the source code for detailed information.

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc