run a program
run a program, edit
run a program, edit, make an edit, run | edit takes effect
run a program with error | big picture
run a program, edit, make an error, run
run a program, edit, ^g to a different definition, make an edit, ^e to run again
run a program, edit, ^g to a non-existent definition
run a program, edit, ^g to a different definition, ^g to a different definition, ^e to run again
start -> big picture -> edit -> move cursor -> run -> edit | cursor preserved
start -> big picture -> edit A -> move cursor -> big picture -> edit B | cursor initialized
start -> big picture -> edit -> move cursor -> run -> exit -> start | big picture (optional)
start -> big picture -> edit A -> move cursor -> run -> exit -> start -> ... -> edit B | cursor initialized
start -> big picture -> edit A -> move cursor -> run -> exit -> start -> ... -> edit B | big picture
syntax highlighting for line comments
syntax highlighting for multiline comments
start -> big picture -> recent changes -> add note -> save | note visible
start -> big picture -> arrow keys* | always exactly one definition highlighted

It's very important not to leak space on the Lua stack, particularly
proportionate to keypresses. That's a recipe for segfaults.

This implies that bouncing around between big picture, editor, recent changes,
running app.. shouldn't grow the call stack either.

== security/privacy
program draws over menu -> getch -> Teliva menu is still visible

TODO protect sensitive teliva files (teliva_edit_buffer, etc.)
  should we protect .c sources?