Re: doc elisp intro cross reference fixes

[Richard Stallman]

    >     2. A variable defined using a defcustom without a :group _is_ in a
    >        group, the `nil' group:
    >
    > Isn't it a bug for a defcustom to lack a :group?

    It was never intended for that case to be a bug.

But shouldn't every defcustom be part of some meaningful group?
It seems to me that they all should.

    And I don't really see it is as a case where "legitimate" is proper
    word to use.  Nothing breaks if the option is in no group.  And nobody
    benefits from having the option in a poorly chosen group, it may even
    be noise to users of that group.

Every option ought to be in a well-chosen group.  I agree that a defcustom
which fails to specify a group, even by default, should "work".  But I
think it should get a warning, so that the maintainer of the file will
define a group for it.