Update: Callback changes and improvements.

Update: Callback changes and improvements.

The `void *(*)(void *)` function structure is being used so add that as a function callback type `f_void_pointer_call_t`.

Add `fl_print_call_t` function callback type.

Rename the console parameter callback from `callback` to `on_match`.
Add `f_console_parameters_call_t` function callback type.
Fix documentation comment where `length` should instead be `used`.

The `void_main` are now replaced with literal `main` type now that the typedef structure improvements are in place.

Shorten the `callback` name to `call`.
Use more typedefs for functions.
This better takes advantage of how functions are a "first class citizen" in C.