testing all of RBTree.hs in 11s at depth 3
better test harness output
generating more test inputs, but some are invalid!

see RBTree.append
use type in variable name for debugging...
fix bug in constraint generation..

really need to get generic generator working, these things are too fragile..
merge generics branch
add to .gitignore
Merge branch 'master' into ghc-generics
generic gen seems to work, now for stitch..