Add `GHC.OldList` legacy module

Authored by hvr.


Add GHC.OldList legacy module

This module provides access the list-specialised versions for legacy purposes
(such as implementing Haskell2010-ish preludes). This module basically
re-exports the hidden Data.OldList module (but in the less controversial GHC.*
namespace, which signals less committment to keep this module around).

This is legacy module is mostly for GHC 7.10's sake. What becomes long-term
of GHC.OldList can be decided unhurriedly during the GHC 7.12 development

Reviewed By: austin

Differential Revision: