Log Message:
Changes in version 2.4.2

    Added Control.Concurrent.STM.TSem (transactional semaphore)

Changes in version 2.4.1

    Added Applicative/Alternative instances of STM for GHC <7.0

Changes in version 2.4

    Added Control.Concurrent.STM.TQueue (a faster TChan)

    Added Control.Concurrent.STM.TBQueue (a bounded channel based on TQueue)

    TChan has an Eq instances

    Added newBroadcastTChan and newBroadcastTChanIO

    Some performance improvements for TChan

    Added cloneTChan