`TupleTreeReference`s use the Root type as a pointer only so they can
operate with forward declarations. Before this commit there were static
asserts that prevented this use case, and thus required the headers
defining the root type to be included before this one to work correctly.
We drop those `static_assert`s to make sure that all headers are parsable
on their own.
Now all the generated `.cpp` include `Binary.h`. This ensures we don't
trigger the wrong concept due to forward declarations.
Also, this commit introduces a couple of `static_assert`s which should
enable us to early identification of similar problems.
Alessandro Di Federico