Support private fields
Use private fields in tooltip.rkt now
Don't add super-type inits into type with #:extends
tooltip.rkt improvement
Add typed/racket/gui
Add "multiple inheritance" for class types
Allow duplicate type names if they have the same type
More draw and gui types
Fix weird bug with field vs. private
Attempt to allow recursive types in objects/classes

The contract generation is the most brittle part.
I'm not sure this is correct yet.
Type improvements in gui and draw
Convert bitmap-message.rkt