[Squeakland] Set transparent color.

[Blake]

Hey, Squeaklanders--

	I've got graphics from an external source that I'm importing into Etoys.  
However, they have a white background which is coming through rather than  
being treated as transparent. I've resolved this by saving them as GIFs  
and setting the transparent color. But it'd be cool to be able to fix that  
inside of Squeak.

	So...is it?<s>

	===Blake===