### Bug fixes

Fix a bug that could lead to spurious 'inconsistent skip sets' errors.

Fix a bug that caused an unescaped '-' at the start or end of a character set to silently be converted to a nonsensical character.

Fix a confusing behavior where literal tokens declared in the `@tokens` block didn't get names when they started with a lower-case character.

### New features

Top rules may now be defined inside `@skip` scopes.

The parser no longer treats an empty position in a choice operator as the empty expression, but requires an explicit () marker (to avoid a common mistake).