Callback objects (`CallbackObject`) get now bound to callback engine.
Callback objects (`CallbackObject`) get now bound to callback engine.

Calling `execute()` member function function of `CallbackEngine` now
enters the `execute()` member function of each `CallbackObject` and it
also enters the callback function itself. Passing parameters to the
callback does not yet work properly.

Not all tests pass yet.

	modified:   cpp/ylikuutio/callback/callback_object.cpp

nrz/ylikuutio,nrz/ylikuutio,nrz/ylikuutio,nrz/ylikuutio