Ready-made bytes for plotting two-pixel points in the mode 4 dashboard (the
bottom part of the screen). The layout of the pixels is similar to the layout
of four-colour mode 5 pixels, so the byte at position X contains a 2-pixel
mode 4 dot at position 2 * X (we do this so the same code can be used to
create both the monochrome Electron dashboard and the four-colour mode 5
dashboard in the other versions).