Proposal: Add concatMapM function (#2042)

[Don Stewart]

waldmann:
> 
> >>>    3. Opposed to any additions to the base library:
> >>>       - Bulat Ziganshin
> 
> Add me to this list.
> 
> "base" is not a convenience library,
> it should contain fundamentally important stuff.

I think the Prelude is our equivalent here.
base itself is fundamental stuff, plus what we use a lot.

> 
> Cf. java.lang, which "Provides classes that are fundamental
> to the design of the Java programming language"
> http://java.sun.com/javase/6/docs/api/java/lang/package-summary.html
> 
> The emphasis (I think) is on *design* of the *language*.

If the proposal is that nothing new be added to base, that needs
to be done separately. And a case made for why what we have
at the moment is fundamental, excluding all else.

Remember, this is not a discussion about whether things are to be 
added to base -- we did that a year ago, and the library process is
the result.

-- Don