Fix some free variable warnings from the byte compiler

ido-completing-read+.el

@@ -84,11 +84,17 @@ Note that when you update ido-completing-read+, this variable may
 not be updated until you restart Emacs.")
 
 (require 'ido)
+(require 'minibuf-eldef)
 (require 'cl-lib)
 (require 'cus-edit)
 (require 's)
 (require 'memoize)
 
+;; Silence some byte-compiler warnings
+(eval-when-compile
+  (require 'minibuf-eldef)
+  (require 'flx-ido nil t))
+
 ;;; Debug messages
 
 (define-minor-mode ido-cr+-debug-mode