Remove files that should never had been committed.
Fix comments that make haddock barf.
Remove unnecessary LANGUAGE pragmas.
Clean up unit tests.

The unit tests are now organized into logical groups. This should make
adding language extension-specific tests easier.
More code reorganization.

No functional changes.
Replace the '_no_leading_attributes' grammar rule suffix with '_nla'.
Give rules that return RevLists a rlist suffix.
Simplify the translation_unit grammar rule.
Split out a grammar rule for Objective-C interface declarations.
Flesh out support for Objective C antiquoters.

This work is based on a patch from @mageshb.
Bump version number.