Declare some used variables using defvar

This prevents compile warnings about free variables.

ido-ubiquitous.el

@@ -52,8 +52,13 @@
 (require 'advice)
 (require 'cl)
 
-;; Declare this ahead of time to quiet the compiler
+;; Declare these ahead of time to quiet the compiler
 (defvar ido-ubiquitous-fallback-completing-read-function)
+(defvar predicate)
+(defvar inherit-input-method)
+(defvar ido-cur-item)
+(defvar ido-default-item)
+(defvar ido-cur-list)
 
 ;;; Internal utility functions