Fix option parser to be more forgiving

[benl]

I'm trying to build an executable using:

/path/to/ddc-head/bin/ddc \

-basedir /home/erikd/Hack/Darcs/ddc-head \ hello_world.ds -o hello_world

and getting:

ddc error: no input files

Should this work?

---

We should either accept this or give an error.

There are option parsers on Hackage now, perhaps we should snaffle one.