redex: make the depth-based clause ordering smarter
redex: try harder when checking non-terminals

Unfold non-terminals other than the one we're currently
checking, and follow variable references, when normalizing
patterns for nt checking.
Fix embarrassing bug in OO subtyping

Subtyping on objects was unsound due to an attempt to
make the algorithm more clever. This was a good lesson in
the danger of premature optimization.
start the drracket-tools pkg

pull out the drracket/check-syntax library into this pkg
change the recursive contract stronger implementation
to use hash tables instead of association lists
Add spaces between doc links
Fix error found by cky
Clean
Change hash in one go
style
style
authors
docs
build width
help
consistent colors
updated
default search
help
remove debug