[Distutils] Distribute name for the setup() options.

[Lennart Regebro]

A quick look through the Distribute docs shows that we call the
settings we give to setup py various things. Both "options" and
"arguments" and "parameters" (that last is my fault).

We should probably decide on one thing, and go through the docs to
make sure it's consistent. I prefer "option", although strictly
speaking they *are* keyword arguments.

Opinions?

//Lennart