Patch for suppressing demo creation when full version is available

[Alexandre Detiste]

> Hi Alexandre,
> 
> the version i sent may be useful for more complicated scenarios, but 
> ultimately it's your decision, which version to use.

Here I'm stomping over my own code, mea culpa ;-)

> Bye
> Patrick

I guess keeping it simple is best.

http://anonscm.debian.org/cgit/pkg-games/game-data-packager.git/commit/?id=f0b6a22b5950991c7d59ce2fe411618b8f45a705

This tool should really follow the rule of least surprise;
and not starting to download some huge english demo if
user just wants to package the German/French DVD
he has at hand.

If some user explicitely wants this demo,
he can still use --demo / --package flags.


Thanks,

Bye,
Alexandre