Hang interaction with ido-use-virtual-buffers and recentf

[dabrahams]

This took forever to track down!

With flx and flx-ido in your load-path, if put the following in /tmp/x.el and run emacs -Q -l /tmp/x.el, then type "TypeCheck," emacs will hang.

(load-library "flx.el")
(load-library "flx-ido.el")
(custom-set-variables
'(ido-use-virtual-buffers 'auto)
 '(ido-mode 'buffer nil (ido)))
(flx-ido-mode)
(setq recentf-list '("/tmp/TypeCheck.txt"))
(shell-command "touch /tmp/TypeCheck.txt")
(find-file "/tmp/TypedProgram.txt")
(ido-switch-buffer)