Formatting `interactive' strings.

[Johan Bockgård]

The doc for `interactive' claims that "prompts are passed to format".
This isn't quite true (it uses doprnt), and there are some problems:

* Number formatting is broken:

    (interactive "n\ns%d")  <-- C-x C-e 0 RET

        Instead of "0", some garbage number is used as a prompt for
        the second arg.

    (interactive "n\ns%f")  <-- C-x C-e 0 RET

        => error "Not enough arguments for format string"

    etc.

* %X isn't recognized. (Ditto for %i, but it's undocumented anyway.)

* The `#' flag isn't recognized.

-- 
Johan Bockgård