Add helper version of split_jobs that calls C functions

[LivInTheLookingGlass]

Potential API could be:

def run_cjobs(job_name, *args, converters=()): ...

job_name would be the name of the C function, and possibly also its file. converters would be a list of functions to convert the given Python object to a cffi object or similar.

This would probably be easiest with cython, but I don't, as of yet, know how.

If this does work, a similar API should be provided for other languages that can interact with Python or be called from C. I know you can do go, and I'm fairly sure rust would work if C does

[LivInTheLookingGlass]

I think I have something similar to this working in the cython branch. It's not quite the same, and it would have problems if you needed to include any .c files, but it's at least partial support.

Full support would need to build an actual C extension, either using Cython or the standard C API. This is a good first step, though. If I can find a way to compile at runtime with a .c file, then that would be the way to go.