[sane.ds try2 1/3] Get resolution from sane, instead of hard coding -1.

[Jeremy White]

Hi Juan,

>> The other comment is, is adding a new file (option.c) really
>> necessary?  If you're planning to expand it a lot, perhaps, but just
>> for this one small function it looks like overkill to me.
> 
> This remark still stands.

Yes, I am planning on expanding options.c a fair amount,
and I'm going to need that functionality in at least 2 of the existing
files in sane.ds, so I thought it should go in another file.

Cheers,

Jeremy