[patch] New method for scaling wallpaper

[Unai Garro]

> > So I added a new method, which I called "Optimal Fill" (I couldn't find a
> > better name for it, but feel free to change it).
>
> Isn't the effect of "Center maxspect" ?

It's not exactly the same. Maxpect method scales up the image until _one_ of 
the side gets to the maximum size of the desktop. While the other one will be 
shorter than the screen. 

This other method scales the image up, until _both_ sides are equal or bigger 
than the desktop size. The advantage is that you get no empty spaces on 
screen.

see this photo as example:
http:// www! telefonica ! net / web / ugarro / sample.jpg

It clearly shows the difference between maxpect and this method. Also if you 
can see the scale method, that one distorts the image (although that's not 
very clear in this photo)