Adjusted background painting code on Windows for the new container structure.
More TODOs.
Cleaned up some code.
Began the GTK+ backend migration. control_unix.go is migrated; Area overlay changes are done now so I don't forget later as well.
Did most of the GTK+ migration.
Readded containerResize() on GTK+; going to have to figure out how I'm going to do GTK+ size control...
Figured out what to do about containers in GTK+ and applied it to Group.
Migrated GTK+ Window.
Migrated GTK+ Tab. Now to test!
Fixed compiler errors. Now to fix runtime errors! Woo!
Fixed GTK+ Area crash (damn typo). Now to figure out why everything is misplaced :D