Re: wrong new indices accepted

[Karl Berry]

    But then there is the conflict with default indices which have
    one letter index commands and 2 letter names.

Clearly a user-defined index that conflicts with other indices, or other
generated files like aux, toc, etc., should not be allowed.

But I agree, we may as well allow any index name consisting of letters
only.  I'll see if I can get makeinfo to give appropriate errors.

Thanks,
Karl