Pixel diff logic for frame rate improvment now working.
It's still working on a per pixels bases so too slow with full screen update.
Thus it's still disabled.

Trying to optimize our swap buffer implementation by sending only the pixel
block which ave changed. No joy so far.

Restoring some of our on-screen functionality for debug purposes.
We could prove that updating a single pixel is much faster than updating our
whole screen. Single pixel updates runs at full 24 FPS.