Re: keymap inheritance for non-sparse keymaps

[Richard Stallman]

    The only thing changed by my patch, really, is that `make-keymap'
    does not hide the "plain-key" bindings of its parent map any more,
    and it's really unusual to want to do that.  So I'm quite confident
    that it does not break any code (and might even fix some).

Please check whether anything in Emacs does use a non-sparse keymap
with a parent now.  If so, please look at what this change will do.