bug#5777: 23.1.90; find-dired prompt bug

[Chong Yidong]

> emacs -Q
> M-x ido-mode
> M-x ido-everywhere
> M-x find-dired
>
> Bug symptons:
> Impossible to choose directory since 'current directory' (.) is not in
> the ido-alternatives. Pressing return just enters the directory rather
> than choosing it.
>
> Bug reason:
> In find-dired (find-dired.el): The first prompt argument in
> interactive is read-file-name.
>
> Bug solution:
> In find-dired (find-dired.el): The first prompt argument in
> interactive should be read-directory-name.

Thanks for reporting the bug, and investigating.  I've checked the fix
into the trunk.