Fix a few small type mismatches

[cspiegel]

uint64_t isn't guaranteed to be an unsigned long long, so cast in printf and use SCN macro in scanf.

int16_t isn't guaranteed to be a short, so use an SCN macro in scanf.

enums aren't guaranteed to have the same representation as int, so use an intermediate variable.

[angstsmurf]

Thanks! I did wonder what the proper way to do this is.