More TODOs.
Began migrating all the Mac OS X sizing stuff over.
Began cleaning up the sizing/container/control stuff by changing container to sizing.
Migrated the Windows backend to use sizer.
Migrated the GTK+ backend to the new sizer system.
Migrated the Mac OS X backend to sizer. Once I get this control sizing stuff working there and the height of a Tab tab on Windows, I'm going to chuck this whole embedding thing and sacrifice a non-cluttered directory structure for CODE SIMPLICITY.
Wrote Control.preferredSize() (including Tab.preferredSize()) on Mac OS X.
Migrated the Label alignment code back into the Mac OS X port.
Wrote code to get Windows Tabs's tab height; will integrate it later.
Rewrote the tab height calculation function from the previous commit to consider all tabs, just to be safe.
Implemented Tab.preferredSize() on Windows.
Removed the generic preferredSize() from the Windows backend; all controls are now expected to provide their own on Windows (this is really the only way to go there). NOW I can rework the whole control nonsense...