[DPP-72] Unidentified memory leak with -prof/-hc

[qnikst]

[Imported from JIRA. Reported by Tim Watson [Administrator] @hyperthunk) as DPP-72 on 2013-04-11 22:44:19]
See https://groups.google.com/forum/?fromgroups=#!topic/parallel-haskell/vitjH-yzYwY for details.