Low power display for Puck (ST7302)

That works great - many thank s- I did not know you could access the hidden root that way!

I tried another version of the ST7302 driver which uses an image buffer in addition to the screen mirror buffer. This version only copies the updated part of the image buffer into the screen buffer put still blits the whole screen buffer in g.flip.

This version reduces 550ms to 146ms which is much more useable and has better power consumption at the expense of the additional 4000 byte buffer.

The new version is in the repository here. I am sure the update function can be optimised using some of your bithack code.