No Serial output with Serial3

[Finnitio]

I use

#define Serial Serial3 for Serial3 for a AVR128DB48, so Serial output did not work with:

tuner(&input, &output, sTune::ZN_PID, sTune::direct5T, sTune::printALL)

so i added

#define Serial Serial3

to stune.h to make it work.