atrf-path: visualize the limits in GUI mode
atrf-path: visualize the limits in GUI mode

- gui.c (avg2y, segment): moved mapping from measurement to y position
  to separate function, to allow for sharing
- gui.c (LIMIT_RGBA, draw_limit, gui): draw the limits

cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan