[OS X Emacs] mac-right-option-modifier in AppKit emacs?

[Richard Cobbe]

I'm using an AppKit build of Emacs 23 based on YAMAMOTO Mitsuharu's
patches.  I currently have the following settings:

    (setq mac-command-modifier 'meta)
    (setq mac-option-modifier nil)

so meta is immediately to the left of the spacebar, where my thumb expects
to find it, and option is passed through to MacOS, for extended characters.

I'd like to use right-option as super, if possible.  According to
<http://www.emacswiki.org/emacs/EmacsForMacOS#toc23>, I should be able to
say

    (setq mac-right-option-modifier 'super)

but that doesn't have any effect.  Indeed, if I restart emacs to clear the
effects of this attempted setting, then describe-variable doesn't recognize
the variable, and typing M-: mac-right-option-modifier drops me into the
Lisp debugger, because the symbol's variable binding is void (or whatever
the elisp error is; you know what I mean).

Is this a known bug/limitation of the AppKit build, is the wiki page out of
date, or am I missing something?

Thanks,

Richard