gpioCfgGetInternals and gpioCfgSetInternals do not return PI_INITIALISED if it has already been initialised

[berndporr]

According to the documentation
https://github.com/joan2937/pigpio/blob/master/pigpio.h#L107
all gpioCfg functions return PI_INITIALISED after gpioInitialise() has been called but neither gpioCfgGetInternals nor gpioCfgSetInternals do it:
https://github.com/joan2937/pigpio/blob/master/pigpio.c#L14019
gpioCfgGetInternals cannot return an error code as it returns an unsigned int.
gpioCfgSetInternals just returns always zero.
Perhaps just the doc could be updated or gpioCfgSetInternals could return an error if called after gpioInitialise?

[guymcswain]

Your suggestions seem reasonable to me. Changing the API to match the doc is preferred as in this case nobody else appears to be using the return value.

A pull request is welcome with these expectations: If accepted I will merge to the develop branch as soon as I get around to it but it won't make it into master until the next release. I'm trying to limit releases to once or twice per year unless a critical issue comes up. If you pull from develop you'll be getting the latest version of pigpio. I've been pretty conservative by only placing changes in develop that are tested and on track for the next release.