Re: Shift Tab should move backward in help buffers

["Richard M. Stallman" <rms@gnu.org>]

    So it may be more consistent for the defaults to be:

    <S-tab>   aliased to backtab
    <backtab> aliased to TAB

That seems plausible to me, in spirit, but I am not sure it is
possible.  function-key-map operates just once on the input event
stream, and then key-translation-map operates once.  It could be that
on some terminals S-tab is represented by an escape sequence which is
decoded by function-key-map, so there is no way to translate it twice
more.

Thus, clean as this is, we can't do it without creating some
new mechanism.  And I don't think it's worth creating a new
mechanism just for this.

    [I'm not even sure that maintaining a default aliasing of S-TAB -> TAB
    is very important -- this feature is handy for the alphabetic keys for
    several reasons, but I don't think it matters very much for keys like
    TAB.]

I agree with that.  It isn't crucial for either S-tab or backtab to
alias to TAB.