Update the 'optmenu' data file to describe the simple options menu
(new paragraph containing just a one sentence) as well as the full
options menu (still several paragraphs). Visible by choosing '?' in
the full options menu or the 'how to set options' choice in the main
help menu.
Add a line to the simple options menu about how to get the full
options menu. Only shown if you type '?' to toggle on "show help";
taken away again if you use '?' to toggle back to "hide help".
Move the help text for the 'O' command from the code into its own file
and allow that to be accessed from the '?' menu as well as by choosing
entry '?' in the 'O' menu.
sys/unix/Makefile.top has been updated to handle new 'optmenu', others
need to catch up. The game will still build and run without the file
but asking for options menu help won't work until they do.