[gold patch] Add --help and --version options to dwp.

[Cary Coutant]

> Cary> I've added --help and --version options to dwp, although I wasn't
> Cary> quite sure about whether to send the entire usage message to
> Cary> stderr in the case of an invalid option.
>
> I think for GNU programs it is typical to print a short note and a
> suggestion about --help:

Yeah, I figured that's a good idea for a program that has lots and
lots of options, but since my help message is so short, I figured I'd
just go ahead and print it.

-cary