Proposal: Add concatMapM function (#2042)

[Johannes Waldmann]

Neil Mitchell wrote:

> Orthogonality. 

Indeed.

If a proposed function's name is "fooBar",
because it intends to be a combination of foo and bar,
then "foo . bar" is already a perfect name.

I think you'd recognize a useful abstraction
by the fact that it has an obvious "stand-alone" name.
Otherwise, it's not really an abstraction, is it?

Best regards, Johannes Walmann.