TODO's left on gsoc_nci:

* Tests, more tests...

Future TODOs:

* Update the thunk generator to match the current libffi definition of a signature, they are mostly backwards compatible but not 100% compatible.

Quality of life options for the future:

* Use libffi to generate callbacks with any signature instead of the limited current amount provided by parrot.
> Have a thunk generator for callback functions that can be added at runtime, like old NCI thunks were before for systems without libffi.