Some additional improvements for Arduino

Here's a few changes that make things compiler for the Arduino Mega 2560.

With some additional changes (not included) for the Pinoccio Scout board (comparable CPU to the Arduino Mega), I could make the startup banner be displayed. However it should memory allocation errors,  and the terminal wasn't responsive (presumably because of the memory errors, it seems it was trying to print zeroes all the time because the `inputLine` variable was NULL).

For some reason I couldn't get this to run on my Arduino Mega board, but I blame my hardware (USB connection is broken, I was using an external USB->Serial module, perhaps that messed things up).