bug#788: menu indications of key bindings for remapped commands

[Chong Yidong]

> As described in:
>
> http://lists.gnu.org/archive/html/emacs-devel/2007-05/msg01020.html
>
> key bindings defined via remap look odd in menus.

I changed the code so that [remap foo] commands are not displayed in the
menus.

Ideally, we would follow the remappings, but I think this could mess up
the menu cache (e.g., if the remapped-to command is rebound).  So that's
a larger, post-release project.