Proposal: Add concatMapM function (#2042)

[Johannes 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.

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*.

Best regards, Johannes Waldmann.