Volatile fields in the decoders

[Trustin Lee (이희승)]

Hi folks,

Currently, all decoders distributed with Netty define their state
fields as volatile, because I assumed that the decoders might be
placed after ExecutionHandler.  However, nobody seem to place them
after ExecutionHandler because decoding is a CPU bound task.
Therefore, I'd like to remove the volatile modifier if I did not miss
anything.  Please feel free to post your idea - it will be very
helpful regardless whether it's agreement or disagreement.

Thanks

— Trustin Lee, http://gleamynode.net/