1. long-term: support for inner classes. The parser seems to be OK with

1. long-term: support for inner classes.  The parser seems to be OK with
   these, but the type resolution stuff would need to be extended.
   At a minimum, we'd need to update the logic that figures out where the
   class definition lives, since the components of the fully-specified type
   are no longer components of the path; some of them become components of
   the filename.

2. syntax/parser.ss: parser should throw exception rather than printing
   something to stdout on error.

3. semantics/resolve-source.ss: catch error thrown by parser and return
   #f.

   Depends on item #2.

4. Contracts for ast structures?

5. In semantics/semantic-objects.ss, esp. field%, behavior%, use symbols
   instead of strings to represent names.

6. CRITICAL: test cases!

7. Remove local copy of contract-utils and return to PLaneT when feasible.