Implement another part of the generator

Implement another part of the generator

This commit mainly concerns itself with the construction of the closure
table - the closures and the "first" tokens.
The first tokens could be precalculated but I did not want to do that
as that would require to either have a function with some static
variable (which is meh to clean up) or I would have create another
structure and pass it everywhere. It can be added later on.