traceM and traceShowM

[Martijn van Steenbergen]

Hello,

I propose the addition of the following two functions to module Debug.Trace:

> traceM :: Monad m => String -> m ()
> traceM msg = trace msg (return ())
> 
> traceShowM :: (Show a, Monad m) => a -> m ()
> traceShowM = traceM . show

These functions allow tracing in any do-block. I often define them 
myself; I think they are useful in general.

Deadline: 23 October 2009.

Martijn.