RetainerProfiler: Update retainer profiler debugging
RetainerProfiler: Update retainer profiler debugging

Debug code have not been updated for a long time,
now it's changed to it compiles with recent RTS.

Reviewers: bgamari, erikd, simonmar

Reviewed By: simonmar

Subscribers: rwbarton, carter

Differential Revision: https://phabricator.haskell.org/D5369

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