[BUG #6169] minor comment
[BUG #7395] removed multiple occurrences of the same JSDoc warning

- different Generator parts of the Hint-using kind (e.g. dependecy analysis, asset
  calculation, ...) got different trees with clazz.tree(), so hint trees
  were calculated multiple times
- hence the duplication of JSDoc warnings
- put creating the Hint() tree directly into MClassCode.tree() (like the scope tree),
  so it gets cached away immediately, and is available on the next read
- remove string-alikeness of HintArgument, as this somehow collides with
  pickling (again)
[BUG #7395] removed old get_at_hints()
[BUG #7395] removed experimental check/dependencies module