To create a setup screen more symbols are created and added to the
symbol table. Helper functions are added to draw homogenous areas onto
the display. Add two new fields `Click` and `Back` to the `Input`
enum. Adapt functions already handling input to those new kinds of
input. Add the setup screen construct. Add global atomics to handle
the button and the timer for handling the back input when the button
is pressed until the timer one overflows. Button press and the timer
are handled via interrupts.
finga
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