CurlyErrors modified to work with all current test cases. Made to
automatically tester curly brace related errors more easily. However,
it is easy to think of new cases where curly_diagnosis would fail, so
extensibility is an issue.

Test cases and some sketches of the return-related errors are provided in
Returns. However, no files have been compiled yet. A different approach
may be taken than the one suggested by the present files.