[Bro] for loop

[Vern Paxson]

> This is not the first time that this has come up, but generic looping 
> has been discouraged in general for performance reasons.

Now not so much for performance reasons (though that was the original
reason) but to push on users to think about using other language constructs
that achieve the same results using more abstracted data structures.
The notion is that often there's a way to express what you want to
do using sets, tables, or events.

		Vern