optimisation on cancellable threads
optimisation on cancellable threads

Ignore-this: b87791986f924c5b93deba658c1a6002

Use directly the list of threads to cancel with the [Temp]
constructor.

darcs-hash:20100109092938-c41ad-c9a9c58b9e2dc0d1f286769d9434cb5cb0a3a3db.gz

avsm/lwt-OLD,avsm/lwt-OLD