Squashed the delete cue text token function to simplify it.

I've also changed it so that the delete cue text token function accepts a pointer to
a pointer to a token and sets the tokens pointer to 0 upon completion. This will stop
us from trying to free it again once it has been freed.
Merge pull request #185 from RickEyre/squash-token-deletion

Squashed the delete cue text token function to simplify it.