Fix child count and annotation error.

- Child count not matching was caused by a bug in the attach internal node function
where the the two **vars were not being initialized. I simplified the function a
little by removing one of the **vars and using a stand in var for the internal_data.
- The other error fixed was one where annotations were being added to internal nodes
regardless of there type. I've added a function that will be able to tell the cuetext
tokenizer whether or not the tag supports annotations.

Please review @caitp or @rillian.