bug#400: 23.0.60; C-h v should pick up lispified name in Customize

[martin rudalics]

> M-x customize-option Info-hide-note-references
>
> Put the cursor on the unlispified option name:
> Info Hide Note References.
>
> C-h v
>
> The option name is not picked up as the default value. All commands,
> such as `describe-variable', that ask the user to input a variable
> name should use the lispified name as the default value:
> Info-hide-note-references, in this case.
>
> The way this should be treated generally is that `Info Hide Note
> References' should simply be the _displayed form_ of the
> variable. Under the covers, Emacs should always see the true variable
> name.

Look at what I did in `info-lookup-guess-custom-symbol'.  Not that I'm
particularly proud of it.  Maybe you can find a cleaner solution.