tiling possibly xinerama-aware

[Christopher Roy Bratusek]

Hi all,

I added some code to - possibly - make tiling xinerama-aware (Janek said 
on the Wiki it doesn't work properly). Either way, I  can't test it 
under real conditions, so it's kind of one-shot. I'd like to ask someone 
who can test under real conditions to checkout edge-actions-1.9 branch 
and try it.

Chris