Generalize groupBy in a useful way?

[Ross Paterson]

On Fri, Sep 05, 2008 at 07:06:54AM +0000, Bart Massey wrote:
> I think it would be better to expand the definition of
> groupBy such that the equality test is applied only to
> adjacent elements (with the arguments in proper order).

I agree:

	http://www.haskell.org/pipermail/haskell-cafe/2006-October/019148.html
	http://www.haskell.org/pipermail/libraries/2007-August/008031.html

We should do it this time.  (Probably too late for 6.10, though.)