Process ids don't cycle nicely

[pguyot]

Local process ids can overflow.

They are incremented not taking into account the fact that they are encoded on 28 bits only.

If the counter overflows at 1 << 28, we should truncate it back to 1 and be careful to not affect existing process ids. While there cannot be more than 2^28 living processes on a microcontroller, we could have a conflict if a system is running long enough besides the lost bits when encoding to a term.