[Proposal] Add instance Monoid a => Monoid (Const a b)

[Krzysztof Gogolewski]

> > I think this a Monoid instance on Const would be useful.
+1

2013/9/30 John Wiegley <johnw at fpcomplete.com>:
>>>>>> haskell  <haskell at nand.wakku.to> writes:
>
>> I think this a Monoid instance on Const would be useful.
>
> +1
>
> --
> John Wiegley
> FP Complete                         Haskell tools, training and consulting
> http://fpcomplete.com               johnw on #haskell/irc.freenode.net
> _______________________________________________
> Libraries mailing list
> Libraries at haskell.org
> http://www.haskell.org/mailman/listinfo/libraries