TODO

* Have compile return a Stats record of timing etc
* In interactive mode, make the runtime system catch ^C and stop execution
* Type checker improvements:
  - allow generalization for local bindings
  - use subsumption (like if) in the arms of alternatives
  - instead of skolemization, use regular variables, making sure they are unique
* Redo type synonym expansion
  - Do expansion during unification
* Implement two level tables for instances even in the tricky cases
* Removing [] from prim table
* Use pointer reversal during marking, will be slower
* Fix bug uncovered by Data.Type.Equality
* mkQIdent
* Get rid of evalstring()
  - do everything in Haskell
* Better pretty print of Expr
* Implement qualified constraints
* Use capi, add value and field modifiers
* Ad hoc fix for f.g: check if g is a field
* Divide lib into different packages
* Sync lib with GHC base
* Use finalizers for alloca?
* Better naming of internal identifiers
* Add mask&co to exceptions
* Make a Unicode version of Data.Char
  - make tables using the Haskell tools
  - read tables lazily when outside ASCII range
* Add EmptyDataDeriving

Bugs:
* Check for escaping skolemized variables
* Type checking Data.Data
* let needs {} in a do with {}
* export list in -boot doesn't work
* overloaded PatBind is totally wrong
* newtype deriving Semigroup is broken