Bugfixes, bugfixes:

  - allow compiling expressions in the context of any module we have
    an interface for, including "Prelude".
  - don't forget to pull in things like unpackCString# in the renamer,
    we might need to use them for desugaring Strings, for example.  I'm
    sure there are other things we'll need to pull in too.
  - :quit now works from the interpreter (!)