8.0.0: Annotations and comments rework

This major release promotes annotations and comments to Node subclasses, making it easy to implement different emitter scenarios for them. For example, classes to be used with the XP Framework will have meta information attached to them, while others will not, reducing their dependencies.

• Merged PR #35: Support static closures (static fn() => ...) - @thekid
• Implemented xp-framework/rfc#341: Drop XP 9 compatibility - @thekid
• Merged PR #34: Refactor annotations from associative arrays to instances
  of the lang.ast.nodes.Annotations class.
  (@thekid)
• Merged PR #33: Refactor apidoc comments from bare strings to instances
  of the lang.ast.nodes.Comment class.
  (@thekid)