Proposal: Add the orphan instance Monoid e => Monad ((, )e) to Data.Monoid

[Paterson, Ross]

Bas van Dijk writes:
> BTW, it would be really nice if transformers could change its WriterT type from:

> newtype WriterT w m a = WriterT { runWriterT :: m (a, w) }

> to:

> newtype WriterT w m a = WriterT { runWriterT :: m (w, a) }

> so that it becomes compatible with the proposed ((,) w) instance.

> Ross, any chance that this could be done. Or does this break to much code?

Just every module that uses WriterT, runWriterT or runWriter.  Is the neatness worth it?