Experimenting with Cython.
- counter: runs simple Python functions from C
- events: event system implemented in Cython, allows users to define Python event handlers triggered by C
- callback: passes Python functions as parameters to C functions accepting function pointers, using a callback mechanism
- ctypes (WIP): implements ctypes-based callbacks to pass Python functions as parameters to C functions
- kwargs: passes keyword arguments to Python functions from C
- add callback example
- add a callback example that uses ctypes-based callbacks, like in Cubature
- consider sophisticating the events example by adding decorators such as @once