bug#5777: 23.1.90; find-dired prompt bug

[Stefan Guath]

emacs-version: GNU Emacs 23.1.90.1 (x86_64-apple-darwin10.2.0, NS 
apple-appkit-1038.25) of 2010-02-23

To trigger bug:
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.