lisp/ob-clojure.el: Fix header argument :var binding

* lisp/ob-clojure.el (org-babel-expand-body:clojure): Always quote
the variables passed from org-mode in Clojure let binding.
When a variable is a table or list, it's value is "(..data..)"
and without quotes, Clojure would try to execute the first
value as a function.

lisp/ob-clojure.el

@@ -133,7 +133,7 @@ or set the `:backend' header argument"))))
 		   (format "(let [%s]\n%s)"
 			   (mapconcat
 			    (lambda (var)
-			      (format "%S %S" (car var) (cdr var)))
+			      (format "%S '%S" (car var) (cdr var)))
 			    vars
 			    "\n      ")
 			   body))))))