Restore the ability to select extended commands by keystroke.
The key translation stuff had gotten attached to the wrong widget.
When using keys to highlight an entry in the extended command menu,
don't reset the key-by-key handling so quickly. (On second and
subsequent keystrokes, if you waited more than 0.5 second, the new
key started picking an extended command from scratch rather than
continuing the current one, making it pretty hard to disambiguate
commands which have the same initial letter. Now the delay
threshold is 2.5 seconds. In theory that should become a user-
preference resource but I don't think it's worth the effort.)
Display the help choice in response to '?'.
Clean up the formatting of the top two buttons (dismiss + help).
Start with a scroll bar if the menu is too big to fit on the screen.
Prior to this, on OSX, the full menu would be constructed but any
of it that was 'displayed' beneath the bottom of the screen was
inaccessible because it couldn't be dragged higher and couldn't be
resized to get a scroll bar (since the way to resize on OSX is by
dragging the bottom right corner--which was off the screen).
The problems I mentioned recently are still present: when scroll
bar is present, I can click beneath it and it moves down, but
neither dragging it up nor clicking above it will move it back up.
Fortunately the recently implemented up and down arrows both work,
even after clicking/dragging starts failing.
There was a lot of trial and error involved here. Most of it
eventually got phased out, but the mystery of 'defaultDistance'
(which is reported to be 0 but is actually 4) remains. The screen
height stuff at the end ought to be fixed up if someone can figure
out how to get the width of a horizontal scroll bar or the height
of a title bar. (I'm sure I used to know how to do the latter,
but that was 25 or so years ago, and in Fortran with Xlib rather
than Xt or Xaw....)