Function: easy-menu-filter-return

Convert MENU to the right thing to return from a menu filter.
MENU is a menu as computed by `easy-menu-define' or `easy-menu-create-menu' or
a symbol whose value is such a menu.
In Emacs a menu filter must return a menu (a keymap), in XEmacs a filter must
return a menu items list (without menu name and keywords).
This function returns the right thing in the two cases.
If NAME is provided, it is used for the keymap.