Feature, implement :main command

[Ross Paterson]

On Sun, Oct 30, 2005 at 02:07:30PM +0000, Neil Mitchell wrote:
> > Well the Main module probably imports System.Environment anyway
> Mine never does, I always import System, which doesn't include withArgs

Haskell 98 libraries?  How quaint.

> > The usual way to parse arguments to Hugs commands is readFilename(),
> That does make it much easier, and much shorter, attached is a new
> version. If no one has any objections I'll check it in.

This differs from setArgs in that it leave the args set.  Maybe the
command should just set the args.