tttocea608: add roll-up modes
In roll-up mode, the element expects input text without layout (eg new lines), and the characters it outputs are displayed immediately, without double-buffering as in pop-on mode.
Once the last column is reached, the element simply outputs a carriage return and the text scrolls up, potentially splitting words with no hyphenation.
The main advantage of this mode is its simplicity and the near-zero latency it introduces.