Menu: underscore keyboard shortcuts

This highlights the one-character keyboard shortcuts (i-l-s-p-h-a-q)
which are available as an alternative to the F1 .. F10 keys.

Again thanks to Mohammad Etemaddar for this suggestion.
Menu: exclude 'quit' from arrow navigation

This wraps navigation to cycle from 'info' to 'about' and back,
avoiding accidentally exiting the program when exploring.

Thanks to Mohammad Etemaddar for this suggestion.