Few changes to GHC API:

  * The Instance type is removed. Each instance is represented as dictonary Id.
Now there is:

  isDictonaryId :: Id -> Bool

predicate which allows to distinguish them.

  * The full list of all available predicates of type (Id -> Bool) is exported
  * Few predicates for TyCon are exported
  * checkModule is removed. It isn't used anymore. Instead the full load is made.
The hook API will be required at some time in order to make available the
parsed/typechecked source.